You're complaining about a healer... HELPING ALLIES. 9 times out of 10 it will be in their role (and their characters best interests) to do so. Yeah it's annoying, but it's hardly more annoying than half the affects you can get hit with when you're actually fighting someone in a normal pk situation.

Not only that, but you're comparing it to someone attempting to either grief or kill lowbies by plaguing and summoning assist mobs. You know, possible xp death?