Regen on pull / mid pull is just sloppy. If you are doing it then please go back to class 101 for aggro management. Let them do their job, while some tanks can adjust you have no idea what your going to get in a roulette. Saying this behavior is fine is perpetuating bad game play. if the tank has to be healed then do so with a instant or swift cast + heal after they get aggro and before the next group is in range.