This is an easy quest and all my toons have gotten credit every single time. I just grab one of the mobs send him into the crowd and aggro one, have him walk 30 yards or so to attack another and aggro a lot more. Then I click on him and watch h is health. When he gets to about 3000 I explode his head. usually takes 2 or 3 times to finish killing all the mobs I need but it is like 10 minutes work.