Boss parries, expertise, and incoming damage.

According to WWS parses, a lvl 73 boss parries ~15% of a players' attacks. (thx Worldie, everlight)
According to Wowwiki, a parry increases swing speed by 14-50%.

Assuming an average swing speed increase of 33%, a bosses 2.0 swing would then occur @ 1.33. This results in a 50% increase in incoming player damage.

If 15% of a player's attacks are parried, that means 15% of the time, the bosses incoming damage will be increase 50%.

The average increase in boss damage due to parries is then: 7.5%, or 0.5% increased incoming damage per 1% of boss parries.

Expertise reduces parry chance by 0.25% per point of expertise. This reduces the boss gain in damage by .125% per point of expertise. Thus, each point of expertise roughly(reciprocals change it somewhat) reduces incoming damage by .125%, and 8 points of expertise reduces incoming damage by 1%.

3.9 Expertise Rating = 1 expertise, so it requires 31 points of Expertise Rating in order to reduce boss damage by 1%.

Weapon Expertise talent reduces incoming boss damage by .625%.
Human Racial bonus reduces incoming boss damage by .625%.
2.3 badge bracers(22 exp. rating) reduces incoming boss damage by 0.7%
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Most of the WWS reports tell that bosses' chance of parry is like 12-15% actually, not that 5% stated by wowwiki.
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oh very nice info, so, expertise no just help in hit, in mitigation too.

That's a real strange behaviour. I've noticed these high amount of parrychance mysel and asked some theoryfreaks in my guild. But the answers was the fight duration is too short and that it would just a coincidence with bad luck.

What do we know really? is the base chance to parry 5%, increased by three levels up to 5,6%? Increased by a higher weaponskill versus lower defenseskill up to what, 6,5%? 15-6,5=8,5% coming from a special parry ability for bosses?

Any proofed feedback would be very appreciated!
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Sorry I have no proof to provide you, but do have a hypothesis to share with you.

I hypothesize that it works very similarly to the miss (aka +hit) chance mechanic (or kind of like crushing blow mechanics) such that there is a balloon effect that occurs when a mob is 3 levels above the player.

The alternate hypothesis would be that every level above the player contributes a fixed amount of additional parry%.

To test this, would be easy enough to test on a series of heroic bosses (lvl 72) then test on a series of 25 man bosses (lvl 73) with no +hit gear or talents.
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Mavrix
BE Tankadin
Dalaran

http://www.wowarmory.com/character-sheet.xml?r=Dalaran&n=Mavrix

There's a levle 73-mob in Nagrand that should be doable to try out for testing the parry-rate vs level 73.
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I may be wrong, but didn't they change the human racials from weapon expertise to crit % in 2.3?
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Why don't you take an even easier approach?

Weaponskill should reduce the chance of an enemy-parry. So look for mobs of lower levels, which have a low chance of parries due to their lower defence compared to your weapon-skill.

2,5% parry-reduction leads to another needed reduction of 2,5% vs lvl 70.
With (70-moblevel)*0,04%*5 you get the reduction in parry-chance for a given moblevel.

A mob of lvl 58 has his parry-chance reduced by 2,4%, leaving 0,1% chance left.
A mob of lvl 57 has his parry-chance reduced by 2,6% leaving 0,0% chance left.

So go for the blasted lands and whack at those invulnerable mobs at your hearts content.
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0/43/18

But the big question is, does the mob have 5,6% parry as we are led to believe by theorycrafting or does it have 15% which seems like sometimes through WWSes?
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It's somewhere around 15%. The anecdotal evidence suffices as proof in this case, as it's much, much more often than not, particularly on the bosses that don't use abilities with cast times (as they can't parry while casting).
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Me, LOL!

So, here's another question to ask:

Is the 15% parry something special for raid bosses(like crushing blows), or is it simply that the parry table we have is wrong, and that parry chance jumps at 3 lvls of difference like hit rating and spell hit rating?

eg. does a lvl 70 player have 15% parry vs. a lvl 67 mob?
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