Fix healer AI

Time and again since you've "improved" healer ai I've seen a healer abandon a group of 10+ wizards to heal 1 or 2 that are randomly off to the side. I've seen a healer heal an undamaged wizard that is shooting at a wall while right beside her there is a large group taking fire. I've had 4 healers follow the bk around and completely ignore huge groups of wizards taking fire. I even spawn the healers far from the path of small groups or the bk and they will fly away from a large group taking fire to heal the bk.