I have to admit, I main healer myself, but not all the time can I predict when a pack of mobs is going to die. Sometimes I throw a regen out and I realize it's right as the last mob dies, I have a slight lag issue with my connection. I hate when this is the case, as I don't like the tank having to run in with regen, but I'm always glad to see when a tank does click it off. I never cast when they are running to pull, unless I'm scholar or in nocturnal sect (the shields can make a difference) and only when I know the cure will hit before the mob is pulled for a shield. But never a regen.