Here's a thought. Get your tank to... I dunno... ... TANK!!!!!
I rarely use my knock back in pve because the tanks I run with know how to tank.
If you rely on your KB in pve you are doing something wrong.
I take it you have never actually tanked.. Besides, relying on someone else is never a good idea.. Like healers, tanks have enough to worry about.. Not to mention we can only do so much..
So here is a thought.. Roll a tank before you tell tanks what to do..