First off, you cannot become completely uncrittable. However, according to WoWwiki, you can reduce your chance to be crit to less than 0.1%, which is very valuable for preventing burst damage which your healers cannot keep up with.
http://www.wowwiki.com/Formulas:Defense
Everything I have seen suggests that tanking mechanics are largely unchanged from pre-BC, even though druid class mechanics have been changed substantially. A boss 3 levels higher than you will still have a 5.6% base chance to crit you, and warriors can still use Shield Block to push crushing blows and crits off the hit table. Lacking the Shield Block tool for preventing burst damage, it's important that druids tap whatever we can to minimize our chance to receive burst while tanking if we are to remain competitive tanks.
How to Become Uncrittable
There are three ways to reduce your chance to be crit:
The first is to pick up the Survival of the Fittest talent, which every serious bear tank should have. SotF reduces your chance to be crit by melee by 1/2/3%. The value of this talent is immense due to the high item point cost of crit reduction. This talent is worth 120 Resilience or 180 defense in terms of anti-crit. Not having to get all that resilience or defense means that more item points can be spent on things like armor, agility or dodge, which yield more overall mitigation at a lower item point cost.
The second is to get resilience. 40 Resilience rating will reduce your chance to be crit by a melee, ranged, or spell attack by 1%, and reduce the damage of a crit by 2%. You might think that this stat has extra value for applying to spell attacks, but you'd be wrong. All my testing suggests that mobs do not crit spells. Although resilience will reduce your chance to be crit for fewer item points than defense rating, defense rating will actually yield better overall mitigation. Resilience is meant to be a PvP stat, not a tanking stat. Nevertheless, there are many good tanking items which have resilience, such as the Mok'Nathal Clan Ring, and Resilience is a very viable way to get more crit reduction if you can't get enough defense.
The third is to get defense. 60 defense rating will provide 25 defense skill, increasing a druid's dodge by 1% and reducing your chance to be hit or crit by melee by 1%. Although resilience will get you more crit reduction for fewer item points, and despite the fact that paladins and warriors get more mitigation out of the stat, defense is the best way to increase your mitigation while reducing your chance to be crit because of the extra dodge and miss chance. Altogether, defense gives roughly twice the total mitigation as resilience per rating point.
Balancing Your Tanking Stats
The first step to becoming uncrittable is to take Survival of the Fittest. This talent reduces a level 73 mob's chance to crit you to 2.6%. The rest has to be covered by defense and resilience. To cover that last 2.6% with defense takes 156 defense rating, or 104 resilience rating, or a combination of the two. The defense also gets you 2.6% increased chance to be missed or to dodge. The resilience gets you nothing more outside of PvP.
It's valuable to know that in terms of item points, 10 armor = 1.5 stam = 1 agility = 1 of any rating. That's right, all ratings cost the same amount in the item budget.
The hierarchy in terms of overall survivability for stats relative to their item point cost goes:
Stamina > Armor > Agility > Dodge Rating > Defense Rating > Resilience Rating
This means that while defense and Resilience are good for reducing burst damage, they're terrible long-term mitigation. If you spent item points on 120 resilience to get the 3% crit reduction you should be getting from Survival of the Fittest, you could get 120 agility for the same cost and get 8% dodge, plus 240 armor!
The point is that anti-crit is something you should get, then move on as soon as possible. Don't stack +def up to the moon, because after you have 156, you're wasting your time.
It's also valuable to be mindful of this hierarchy when selecting gems or enchantments. Don't spend all your time at Halaa saving up for that +10 resilience gem when you could use a +8 defense gem for more mitigation at the cost of a little crit reduction, or a +8 agility gem for best overall mitigation. Similarly, the +12 defense rating bracer enchant is worth more in terms of item points than the +12 stamina enchant.
I hope you hardcore druid tanks enjoyed my wall of text. I'll return to it later to make any necessary corrections and try to clean it up a bit. Found sneaky bug.
He is fast, and is the danger.
source :
http://forums.worldofwarcraft.com/threa ... 0117&sid=1
