I think you guys are giving the poster too much credit. Do you guys even thing he is using /assist? not me. All he did is cast a little spell on a mob that the MT had no aggro on, why does he then come after me???? Why do I keep dying, use /assist. If you don't know what this means.
Select main tank, wait till he has pulled and has the mob stopped and has just started to beat on him, type /assist (make a hotkey even better). Then cast to your hearts content, when that mob is finished, do it again! Select the MT(use F2-F6 keys, F1 is you), then type /assist again and I promise you will never get aggro again.
I am in my mid 40's now, and you wouldn't believe how many people still don't know how to assist properly. Most people assist on the first mob, but as soon as the first mob dies everyone just clicks on the pile and start to attack.
I was grouping in DL a while back, My ranger was MT this warrior came along and he kept stealing agro from me even after I pulled with a Bow then snared, usually this is more than enough for me to keep aggro. He was taking a thrashing, he was slightly low level to be in DL. Finally I asked him, are you pushing you taunt button, and he said yes I am trying to train it, I didn't think it would matter. I said that is why you are getting hurt. He said "oh" I didn't think it mattered. Now how does someone not know they are getting aggro, after playing the game for 40 levels. Anyway, I bet my reputation that this poster is not assisting, even if he says he is.