I will very much disagree with healers not standing close to boss. I play this game as healer on savage and ultimate level. I always stick to the boss because that way the aoe heals reach everyone including the tank and meele players. Usually ranged players also stick close to boss because it is understood that healers have range on aoe heals and if you are very far out, you might miss the heals. Only reason to go that far out is for spread mechanics, that's really it.