how much avoidance you have AND how much def you need/got to spare:
/run local b,d,p,r,a=GetBlockChance(),GetDodgeChance(),GetParryChance(),GetCombatRating(CR_DEFENSE_SKILL) a=1/(.0625+.956/(r/122.9625)) ChatFrame1:AddMessage(format("Unhittable: %.2f%% Avoidance: %.2f%% Defense %+.0f rating",b+d+p+5+a,d+p+5+a,r-689))
will update when i find more usefull macros for tanks;)