As long as you get your total Avoidance to 102.5 you will be uncrushable. You can use all different gear to do this.
/script DEFAULT_CHAT_FRAME:AddMessage("Need 102.4 combined avoidance. Currently at:",0.8,0.8,1)
/script DEFAULT_CHAT_FRAME:AddMessage(GetDodgeChance()+Get BlockChance()+GetParryChance()+5+(GetCombatRating( CR_DEFENSE_SKILL)*150/355 + 20)*0.04,1,0.5,0)
That macro will tell you what your exact avoidance is, depending on the state of your character ( If your buffed or unbuffed etc.)