The issues I have with crush through are:
1)  It punishes manual blockers as well.  It in effect removes your RMB from the game.  If you don't see how removing someone's RMB is stupid then I dunno what to say.
2)  It crushes through chamber blocks.  If I chamber your overhead, I worked harder than you did and deserve my parry + hit.  Not to just get crushed anyways.  It's dumb.
3)  It doesn't take my shield skill into account.  I have 7 shield skill.  Not 2, not 3 like guys that just put enough in there to pick one up as they advance with their 2her, but a significant investment into the skill.  Coming up against a crush through user is like someone saying "Yeah, those 3 extra stat points you could have had, they were wasted."