Avoidance or Block Value?

Well, same question as in previous threads but now from me: Where do I go from here?

Armory link: http://eu.wowarmory.com/character-sheet.xml?r=Zirkel+des+Cenarius&n=Rahandra

I am thinking about exchanging weapon enchant against weapon chain for the 28 hit rating, exchanging my boots for http://www.wowhead.com/?item=40743.

Now the real question is: avoidance or block value? I am at 107,something avoidance. Should I still push this higher or should I go for more strength to raise threat / Shield Block Value? And If so, anybody having tips for the SBV?

First off I don't know where you got your numbers from but you're way off. After taking into account diminishing returns on miss you have 100.21% towards the block cap. (Block chance is not avoidance).

Gemming for Hit is wrong, very wrong. You should be using those yellow slots for defense or defense/stam gems.

Now that you are precipice of being block capped you should be looking to replace block rating with defense. That's right, you don't drop defense when you hit the block cap, you drop block rating and stack defense.

Boots are a great upgrade btw.
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Okay, it seems I picked up a bad macro in one of the threads before.

But after some calculating I am even more confused by now.

Using Harlekins Spreadsheet, I am getting something like 102,1, calculating myself I get something along your result 100,3.

Hrmpf and I thought I already reached it. *grml*

Okay, but then to your other statement. Why stacking defense? Because it raises both avoidance stats? Also why is gemming hit wrong? I mean who doesn't love to see his frisbee going everywhere except to the intended target? Also missing an RD sucks big time. Don't get me wrong, I am not complaining. I would appreciate some insight here as I am wondering whe gemming hit is so very wrong?
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In equal amounts always prioritize survival over threat.

You are not a dps, you don't need more threat than is just enough to hold off the DPS.

Defense is prefered becasue it provides slightly less avoidance than dodge but nearly 30% more towards the block cap than dodge. Once you are at the block cap any additional block rating is pushed off the table (for boss tanking only, on trash having additional block rating is often useful).

simply put, it is more effecient to maintain the block cap through defense than trying use a balance of dodge and block rating.

If you don't want RD to miss get the glyph for 100% taunting success (assuming the wonky RD mechanics don't mess it up but it won't be due to a miss). You can survive a missed shield throw quite easily. If your dps aren't waiting to open up on mob till they are next to you, you should yell at them for it. You like, every other tank has a small chance of your pull ability missing.
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Okay, playing around and gemming for survivability (www.chardev.org/?template=109515) and I end up with the following stats:

defense rating 733
dodge rating 184
parry rating 131
block rating 261
agility 120
strength 1067
stamina 2078
block value 939
armor 23564

This brings me to: 103,13 after DR. That looks way better, I agree. And now stacking even more defense?
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Did you account for DR on miss (in the range of 1.5-2% which most calculators do not take into account)?
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I reserve the right to refuse service to those that do not read the stickies.

Well, according to Harlekin's post the sheet does calculate with DR.