Klimpen's 4 Step CopyPasta on Tank Gearing.
I posted this as I'm sick of writing the same thing out in every Tank Gear argument. I felt I should share it, not only because I thought it could be useful for other people (so they don't have to write it), but also so I could get some feedback on if I should change some wording/whatever.
Feel free to change the threat stuff around for Warrior Tanks and use it yourself.
Edit: Clarified point 2 on Uncrushability.
As a Tank, you've got few goals in gearing yourself for raids.
1) Uncritable, 490 Def. Removes the chance for a 200% damaging attack from the attack table.
2) Uncrushable, 102.4% Avoidance (Miss/Parry/Dodge and Block) with abilities active (ShieldBlock/Holy Shield). Removes the chance for a 150% damaging attack from the attack table.
3) Effective Health, giving yourself enough Sta/Armor/BV to survive any burst damage. After armor/BV, if the boss does 9k burst as a maximum having more than 9001 health is wasted. While that's a fairly extreme example, and I personally premote having a comfortable amount of extra Effective Health, it shows that there is such a thing as too much health.
4) If you're dieing because healers are going OoM, there are two things you can change in your gear.
4a) You can increase your threat via addition of +damage or threat enchants. This allows DPS to do more damage, faster. If you've got a threat lead, and none of your DPS'ers are holding back, you don't need more threat. More damage reduces the length of the fight, and therefore the amount of healing needed.
4b) If you've done all the other things above, Uncrush+Uncrit+Enough EH+Enough Threat, then you add in pure avoidance. I put this point last, as it's the least important. It's more important to max out threat/EH in my opinion, than it is to reduce how much healing the healers might have to do. I say might because you can't rely on avoidance, and your healers may have to do an equivalent amount of healing over some periods of the fight than if you had a lower avoidance total.