To clarify the following statement that I made regarding the "490 defense cap" in this post:
490 is also the CAP for defense in relation to critical strike mitigation (unless they raise the maximum mob level beyond 73). Tseric was quoted as saying, "At 490 defense, the math caps out.
490 defense is the cap for critical strike mitigation only (confirmed by Tseric on the US WoW boards). You will still get miss, dodge, parry, and block (14.7875 defense rating for 0.25% to miss dodge parry and block, 1% total mitigation/avoidance). You will still benefit from defense past 490. At 490 defense you become uncrittable to any mob in the game. After reaching 490 you want to work towards raising your block% + dodge% + parry% + Miss% to 100% total so that you will be immune to crushing blows.
Block is technically the most efficient way of raising mitigation, but it is also the hardest to obtain since it’s not really found on a whole lot of things or chantable. Dodge is second I would say because it’s raisable via agility as well as +dodge (ratio isn’t that bad either). Dodge is nice because dodging means you recieve no damage. (I need to double check my ratio formulas for tanking stats, don’t think some are correct).