Just remember - you don't need 490 defense to do heroics (490 is uncritable to a level 73). The bosses are usually level 71 or 72. You are better off going with more stamina. Also level 72 mobs don't crush either. The trash is usually what hits the hardest. 4.5K a shot is pretty common - you need a lot of CC in heroics - you just can't tank 2-3 guys with that gear.