The required Defense to be uncrittable has not been changed:
Raids (lvl 73 boss) - 490 Defense
Instances (lvl 72 boss) - 485 Defense
Crushing blows are no longer a factor in raiding Blizzard changed mechanics so that only enemies 4+ levels above you will crush. Raid bosses are only 3 levels above you, so you no longer need to worry about getting 102.4% avoidance to avoid crushing blows (though for a Warrior this was never much of an issue anyway, unless you were trying to be crit immune without Shield Block up).