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Faction Champions AI Behavior: A Definitive Analysis

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Faction Champions AI Behavior: A Definitive Analysis

Postby Joanadark » Fri Nov 06, 2009 8:02 am

I initially was planning on posting this in the guide to Faction Champions thread, but felt it was significantly important enough and different enough to warrant it's own thread.

Background: Ever since the Faction Champions encounter was released, I have been making it a particular project to understand and codify the AI behind these foes, in order to better perfect the process of controlling this seemingly uncontrollable encounter. After many weeks or pouring over frapses, parses, and testing individual concepts on my own each week.

While I am still attempting to work out the exact formula for their threat determination, the exact numbers are by and large unimportant. The important part are the general concepts behind the way their threat functions.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

General Concepts

The first important point to understand about faction champions is that nothing is random, as much as it may seem so upon first learning the fight. Every action the mobs take is governed by very specific rules, all of which may be controlled to your favor by understanding the priority system behind their AI.

The most important principle to understand is that all the Faction Champions are governed by threat. It is often said that they have no threat table, but this is a myth. You can even see their threat table on omen when you target one of the mobs.

How is this testable?
Look at omen while targeting a Faction Champion. Observe the fact that threat drop abilities such as Feign Death or Fade work as normal on Faction Champions, even on Heroic Difficulty. Observe the fact that taunt effects function as normal on Normal Difficulty, indicating that threat rules exist and can be manipulated using the normal tools, even if they function according to unusual rules.


The cause of the misunderstanding that Faction Champions have no threat is the fact that their threat is not the result of damage taken or healing sensed. It is calculated by different rules than any other encounter in the game.

These are those rules.

~~~~~~~~~~~~~~~~~~~~~~~~~

Melee DPS Champions

Melee DPS Faction Champions calculate their threat based on an additive combination of 3 factors. Each of the three appear to share equal priority for determining target, and the threat list constantly updates.
These factors are ARMOR, PROXIMITY, and HEALTH DEFICIT.

ARMOR
Armor is the first factor of targeting priority and refers to the exact armor value displayed on your character tab. The lower the absolute value of armor on a potential target, the higher the threat.
LOWER ARMOR = HIGHER THREAT

How is this testable?
Have two warlocks stand exactly on top of each other. Have them both activate the spell Fel Armor. Warlocks are one of the highest priority targets in general for Melee when all other factors are equal because they have one of the lowest relative armor values. At some point, one of the melee will be almost guaranteed to target and attempt to attack one of the warlocks wearing Fel Armor. When that happens, have the warlock who was targeted activate Demon Armor, which grants greatly increased additional armor value. Unless outside factors interfere, the melee DPS Faction Champion should always immediately switch targets to the other lock standing in the same spot as the first one, due to the lower armor value.


How does this knowledge help me?
Depending on the class, the understanding of Armor Value's contribution to the aggro calculation can be exploited in various ways. One of the most universal is the ability to have your more vulnerable raid members pre-pot an Indestructible Potion right before entering combat, granting them an additional 2500 armor and thus a much lower threat signature. Similarly, a player who finds themselves vulnerable and unable to escape a melee DPS attacking them may re-actively use an Indestructible Potion to help them drop threat.
Tanks attempting to pick up a target or hold it may wish to put on DPS gear or remove their shield. Players with access to some form of Armor increasing effect such as Inner Fire should pay particular attention to keeping it active at full strength unless they wish to deliberately cause Faction Champions to attack them. Another example is a druid shape-shifting into a higher armor form if focused, such as a feral druid shifting from cat to bear. Warlocks are the class most frequently focus-fired by melee DPS Faction Champions, and their primary threat-signature tool, Demon Armor, was mentioned in the example above.


PROXIMITY
The second piece to the melee DPS Faction Champion threat calculation is proximity; the distance from the Faction Champion to the player. The shorter the distance, the higher the threat.
CLOSER PROXIMITY = HIGHER THREAT

How is this testable?
Have a deathknight Death Grip a melee DPS Faction Champion far away from everyone else in the raid. Then Stun or otherwise CC that Faction Champion. Have any player stand right next to the CC'd Faction Champion, and have everyone else move far, far away. Unless significant outside factors interfere, the Faction Champions will always attempt to attack the player right next to them. For testing purposes, use a class with fairly low relative armor to ensure that the armor and health deficit threat signature of someone else does not override the testing player's proximity threat signature.


How does this knowledge help me?
It doesn't really, since the proper way of handling this knowledge is intuitive already. Melee DPS Faction Champions can only attack you from melee range, and thus it is natural to want to move away from them if they are attacking you. This applies to melee DPS attacking the faction champion too though. It is good practice for a melee DPS who is targeted by a Faction Champion they are DPSing to run away from the Faction Champion and cause it to target switch or to be ineffective at causing any damage until someone else's proximity threat signature overrides theirs and they begin attempting to attack someone else. Reducing as much damage taken by the raid as possible is a primary focus of the entire raid, as the less damage that goes out, the more the healers can focus on dispelling, which results in a far more stable control over the encounter. It is also advisable to keep various forms of snares and movement inhibiting debuffs on melee DPS Faction Champions as often as possible.


HEALTH DEFICIT
The third and final component of a player's threat signature for a melee DPS Faction Champion is their health deficit. This is defined in terms of the absolute value of hp that player is below their maximum hp. This is the factor which causes the seemingly random "insta-gibs" where multiple Faction Champions all target the same player at once and deliver a devastating combination of attacks. This generally occurs when someone takes a DoT tick or a low armor value player is clipped by an aoe effect like Bladestorm. It gives the illusion of intelligence by causing them to attempt to target whoever is weakest in your raid.
HIGHER HEALTH DEFICIT (more damage taken) = HIGHER THREAT

How is this testable?
Have a deathknight Death Grip a melee DPS Faction Champion far away from the rest of the raid. Then Stun it or otherwise CC it. Have two warlocks or roughly equal armor value stand directly on top of the CC'd Faction Champion. Have one of them Life Tap to half health or lower to create a great enough health deficit threat signature to override any minor differences in armor value threat signature between the two warlocks. When the Faction Champion comes out of CC, unless outside factors interfere it will always attempt to attack the warlock at lower health due to the health deficit from Life Tapping.


How does this knowledge help me?
The biggest application of this aspect of the threat signature is focusing a large amount of attention to defensively dispelling DoT and Debuff effects from your raid. The better your raid's dispelling, the more controllable the fight will be because there will be no random health deficits all over the place causing unpredictable target switching to occur. DoTs tick for hard enough to be a significant danger to raid members by setting them up for an insta-gib situation where their health deficit threat signature causes multiple Faction Champions to all switch targets to them at once.
The other aspect of this knowledge that can be exploited is that if you are a tank attempting to control a mob, and you can get a melee DPS Faction Champion far enough away from the rest of the raid that you have a proximity threat signature advantage to compensate for your lower armor value threat signature, if the Faction Champion starts attacking you it will tend to remain attacking you because it will be constantly causing a health deficit on you unless outside factors interfere.
Another application of this applies to warlocks, who should be encouraged to not Life Tap unless positioned a significant distance away from dangerous Faction Champions or receiving immediate healing.


SUMMARY

ARMOR VALUE + PROXIMITY + HEALTH DEFICIT = THREAT SIGNATURE

Note: The rules for melee DPS Faction Champions all also apply to the Hunter and both the Hunter pet and the Warlock pet. Both pets are subject to taunt even in Heroic Difficulty.


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Ranged DPS Faction Champions

Ranged DPS Faction Champions function on very similar lines to melee DPS Faction Champions, with one difference. Instead of Armor Value being part of their threat calculation, they instead compare Resistance to their school of magic.

RESISTANCE + PROXIMITY + HEALTH DEFICIT = THREAT

RESISTANCE
This aspect of the threat calculation is much less noticeable than the armor value part for melee DPS, since resistance levels tend to be the same for everyone in the raid due to raid wide buffs like Mark of the Wild, Auras, and Totems. Some classes have abilities which grant them higher resistance to magic than normal, and will thus tend to not be targeted by the caster Faction Champions, but in general casters will simply deliver killing blow insta-gibs to raid members already being attacked by melee Faction Champions as health deficit is the primary determining factor in their targeting.

How is this testable?
Stun or otherwise CC a caster Faction Champion. Quickly move the entire raid to the complete opposite side of the room so that they will be out of range of that Faction Champion's attacks. Have two players, one buffed with Mark of the Wild, one without Mark of the Wild, stand directly on top of the CC'ed Faction Champion. When the Faction Champion comes out of CC, unless outside factors interfere, they should always attack the player without Mark of the Wild.


How does this knowledge help me?
If you have players which you find are vulnerable to being focused down by casters, have them use a Flask of Lesser Resistance (+50 all resists), which should help significantly to prevent caster Faction Champions from targeting them unless they have a significant proximity and health deficit threat signature.


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Healers

Healers heal based on a very easily recognizable principle. They place priority on their healing targets based on the lowest absolute hp among friendly targets. What this means is that out of all Faction Champions with a health deficit, no matter how big, the one with the lowest numerical amount of health will be selected as the target of their healing. This is why it is relatively easy to burn down high health targets at first, but when they reach lower health all enemy healers will pour massive amounts of healing into the target and it will be much more difficult to finish off.

How is this testable?
Have one player spend the entire fight DPSing the hunter or warlock pet. Since the pets have much lower absolute health than any of the actual Faction Champions, as long as the one player is constantly doing damage to the pet the healers will focus their primary attention on spamming the pet with healing and HoTs. An enhancement shaman is ideal for this as they can purge off the HoTs. Observe the healing received meters following the engagement.


How does this knowledge help me?
Save your CC diminishing returns on enemy healers for when your kill target is reaching lower levels of health, and then chain them in sequence to solidify a kill. As in the method of testing, assign one player, or alternatively all your raid's pets, to constantly DPS the enemy pets. Be sure not to kill them. All heals directed at these pets your interrupters can simply let go through, and save their shocks and kicks for any heals directed at non-pets. This allows you to do a much more effective job at eliminating healing onto your kill target.

LOWER ABSOLUTE HEALTH = HIGHER HEALING PRIORITY

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Conclusion:
I hope this helps those of you out there either working on this fight for the first time, or working towards ever higher levels of tribute all the way up to Tribute to Immortality.
Knowledge is Power.

regards.
Last edited by Joanadark on Fri Nov 06, 2009 9:06 am, edited 1 time in total.
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Re: Faction Champions AI Behavior: A Definitive Analysis

Postby hoho » Fri Nov 06, 2009 8:21 am

LOWER ABSOLUTE HEALTH = HIGHER HEALING PRIORITY
I've still seen their holy pala prefer topping off a hunter's pet who is beating on my holy shield to healing nuke target who is at 15% HP.

There definitely are some kind of basic rules for the AI but they are still relatively stupid. Seeing their rogues blinding temporary pets is not uncommon :)
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Re: Faction Champions AI Behavior: A Definitive Analysis

Postby Joanadark » Fri Nov 06, 2009 8:32 am

hoho wrote:
LOWER ABSOLUTE HEALTH = HIGHER HEALING PRIORITY
I've still seen their holy pala prefer topping off a hunter's pet who is beating on my holy shield to healing nuke target who is at 15% HP.

There definitely are some kind of basic rules for the AI but they are still relatively stupid. Seeing their rogues blinding temporary pets is not uncommon :)


It is important to distinguish the difference between Absolute hp (the numerical amount of hp the target has remaining), and Percentile hp (like in your example, a target at 15%).
What you experienced was almost certainly a case where the cat was at lower Absolute Health than the kill target, despite being at a higher Percentile health.

Additionally, healers do not always follow the exact rule of Absolute health, absolute health merely weights their target selection. They select targets at random, but the lower the absolute health of a target, the higher the probability of it being randomly selected as a heal target.

Healing is the closest thing in the fight to a random element, but it is honestly no more random than the combat table is random. If you have 20% chance to dodge, you have 20% chance to dodge. Your dodge chance isn't random, its fixed and predictable. In the fight, if a target is significantly lower absolute health than all the other targets, the chances of it being selected as the target of a heal are proportionately significantly higher.

This is a controllable and predictable element, not a random one. And it is determined by AI. AI follows rules. It isn't "smart" or "stupid".

Seeing their rogues blinding temporary pets is not uncommon :)


I'm still working on the AI behind CC targeting. It's a lot more difficult to track rules for, so I need a while still before I can plot anything definitive.
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Re: Faction Champions AI Behavior: A Definitive Analysis

Postby Dane » Fri Nov 06, 2009 8:51 am

Amazing info. Mind if I copy/paste and link on my guild forums?
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Re: Faction Champions AI Behavior: A Definitive Analysis

Postby Invisusira » Fri Nov 06, 2009 8:55 am

Dane wrote:Amazing info. Mind if I copy/paste and link on my guild forums?

NO THIS INFO IS TOP SECRET

excellent write-up.

Oh,
The third and final component of a player's threat signature for a melee DPS Faction Champion is their threat deficit.

health deficit I assume you mean.
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Re: Faction Champions AI Behavior: A Definitive Analysis

Postby Joanadark » Fri Nov 06, 2009 9:06 am

thanks for catching the typo. ill correct that.
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Re: Faction Champions AI Behavior: A Definitive Analysis

Postby Joanadark » Fri Nov 06, 2009 9:07 am

Dane wrote:Amazing info. Mind if I copy/paste and link on my guild forums?


Go for it, that's what its here for!
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Re: Faction Champions AI Behavior: A Definitive Analysis

Postby Dane » Fri Nov 06, 2009 9:16 am

Invisusira wrote:
Dane wrote:Amazing info. Mind if I copy/paste and link on my guild forums?

NO THIS INFO IS TOP SECRET


I guess I wasn't clear about my intentions. I'm going to put this on my forums and put "by Dane " on it. Then I'll tell my guild "HAY GUYZ! LOOK WUT I DID!"

Then if they question me, since we've never taken the time to research like this, I'll say "I'm so pro, Blizz gives me an extra raid lockout that I use with my research group, nubs."

Yeah...I'm going to be such a stud.
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Re: Faction Champions AI Behavior: A Definitive Analysis

Postby Joanadark » Fri Nov 06, 2009 9:29 am

Dane wrote:
Invisusira wrote:
Dane wrote:Amazing info. Mind if I copy/paste and link on my guild forums?

NO THIS INFO IS TOP SECRET


I guess I wasn't clear about my intentions. I'm going to put this on my forums and put "by Dane " on it. Then I'll tell my guild "HAY GUYZ! LOOK WUT I DID!"

Then if they question me, since we've never taken the time to research like this, I'll say "I'm so pro, Blizz gives me an extra raid lockout that I use with my research group, nubs."

Yeah...I'm going to be such a stud.


good luck with that. lol.
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Re: Faction Champions AI Behavior: A Definitive Analysis

Postby Belloc » Fri Nov 06, 2009 10:26 am

Joanadark wrote:Additionally, healers do not always follow the exact rule of Absolute health, absolute health merely weights their target selection. They select targets at random, but the lower the absolute health of a target, the higher the probability of it being randomly selected as a heal target.


I think that the healers will always cast heals on the target with the least absolute health. This means that, if they attempt to heal a non-pet, the pet had successfully received a heal and was healed to full when the healer in question selected a target and initiated the cast. Either that, or the kill target's health became lower than the pet's.

Considering the fact that you've got three healers and possibly DoTs being spammed on the pet, that opens up the possibility of the pet being topped off when targets are selected. Also, a Power Word: Shield on the pet is a lot of damage absorbed. Unless dispelled, the pet will be healed to full before the shield is broken.



Now, here's what I want to know: What rules do the pets follow for their targeting? Much like the melee mobs, the pets will quite frequently assist each other in their targeting. Would it be that they follow the same rules and the only difference that I am perceiving is their proximity to other players?
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Re: Faction Champions AI Behavior: A Definitive Analysis

Postby Joanadark » Fri Nov 06, 2009 10:31 am

Now, here's what I want to know: What rules do the pets follow for their targeting? Much like the melee mobs, the pets will quite frequently assist each other in their targeting. Would it be that they follow the same rules and the only difference that I am perceiving is their proximity to other players?


They appear to follow the same rules as melee DPS with the exception that they are tauntable in all difficulty settings.
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Re: Faction Champions AI Behavior: A Definitive Analysis

Postby beornus » Fri Nov 06, 2009 10:52 am

/salute thanks so much, have already posted to guild TOC 10 thread, great stuff!
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Re: Faction Champions AI Behavior: A Definitive Analysis

Postby fafhrd » Fri Nov 06, 2009 11:06 am

I sounds like you killed a couple of warlocks a lot figuring this out brekkie, kudos.
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Re: Faction Champions AI Behavior: A Definitive Analysis

Postby Joanadark » Fri Nov 06, 2009 11:08 am

fafhrd wrote:I sounds like you killed a couple of warlocks a lot figuring this out brekkie, kudos.


I was wondering when someone would pick up on that.
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Re: Faction Champions AI Behavior: A Definitive Analysis

Postby fafhrd » Fri Nov 06, 2009 11:11 am

Btw, did you try testing the effects of debuffing/dispelling/purging/cc on threat? Ie. the reports of bears tanking mobs by spamming demo roar, and whether the mage who's sheeping targets is a preferred target to the mage who isn't?
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