It doesn't sounded like you wanted to blame anyone, I just wanted to clear this up. Though the healer actually is to blame, just not for what some people think.
I think it's far better to teach people how to
proporly use mid-pull Regen instead of silently being annoyed, macroing it off or telling WHm "you don't use Regen pre-pull, never, don't, just stop". If I have a healer doing this but handling it poorly, I simply tell them that while it's okay to do it, they need to stay really close to me in case some of the things you mentioned happened.
It's for their own safety and there is no reason to stand miles away from the tank.