I tank rather than heal, but my strategy dealing with those players is usually to let them die. If they're being overzealous and repeatedly leaping into/pulling groups before I do, I won't do anything until that player is dead. If they won't listen to you, I think that's the next easiest thing to do to send a message. I tend to mostly run with healers I know though so it's a bit easier for me, but I've had plenty of PuG healers ask me to let someone die, and as long as that healer is halfway competent I'm happy to oblige.