IMO, if you're a DPS consistently having to drop what they're doing to help the healer help the tank survive every pull, as well-intentioned as you might be, you should just stop. The tank surviving these encounters is only going to have him think that what he's doing is okay. Sometimes only a good death or two is enough to teach them that they're overdoing it. (That, or they just ragequit after one wipe... which is probably what happens more often nowadays)