This is something the training hall should mention on the healing class. The dmg class talks about aggro pointing out you should hit the tanks target. Healing class should tell the monster get aggro for regen effects you have put on things. Didn't get to tank courses yet, wonder if they mention healers tend to get aggro just by healing.

I was running vault on my DRK and got healer cast Medica II on the start. I politely asked "please don't cast regen effects befire pull" his answer "I know, but it's fun." *shrug* fine, he knows, first pull went ok after I had waited out the regen. On second pull he managed to sneak a regen in in the middle of the pull getting one mob to him I hadn't had time to encage yet. After tanking and killing everything else not touching to the mob even if I well see it he says to chat "archer" to which I told "I know, pulled by your early regen." And left it at that. He didn't pre regen again on the run.