i dont like pre pulls as a non tank, even if my request to pull more gets ignored or rejected, it doesnt give me a right to pull more :P i dont want the tank to be stressed out bc im to impatient.
The only time i do a pre pull is (that is the only exception): if there is a mob walking towards us and the tank doesnt see it coming, only then i hit it and pull it towards him so the healer doesnt get the aggro of it.

PS: im a big fan of tanks who pull a lot but if they dont want to i wont force them.