I'm only 3-boxing, but have a similar setup, Priest/Mage/Warlock. If you're in a situation where you should be pulling, (e.g. SM Cathedral) it's probably not a good idea to send in the voidwalkers.

I also pull with my priest. The way I do it is to pull, attack with the voidwalker, then fade. (Actually my petattack and fade macros are mapped to the same key.) Even with the AoE taunt, you still might need to change targets to get mobs off the priest after the pull.

Since I'm only 3-boxing It takes a bit of time to burn down elite mobs so I have to be careful not to aggro.