I pl alot with my 75 druid and I have noticed that on pulls, if I run by the toon i am pl'ing, sometimes the mobs stop at him and start pounding. For example.... druid runs out and grabs 15-20 mobs, runs back and runs just past the toon being pl'd, druid stops, turns around and gets ready, but half the mobs have now come straight for the wizzy even though he has not casted a spell yet. I think alot of it has to do with the wizzy's lvl and the fact that he is in line with the pull. It could possible be the same thing you are getting. You might want to try to pull and circle the mobs a bit away from the pl'd toon, but still in range for the aoe's if your toon cast them.