Priest Responsibilities

In a 5 man group, what are the responsibilities of a priest concerning:

Healing a warlock every time he restores his mana (while not in combat)

Healing a warlock's pet

Healing a hunter's pet

Doing DPS while no heals are needed (i.e. wand or whatever)

I keep grouping with 'locks who restore their mana and dont bother to eat or band-aid before going back into battle. Isn't that, like, stealing mana from the priest?

And classes with pets will often not bother to heal their pets *at all*. (As in, if I don't heal the pet, the pet DIES. So I usually do. But when the f'kin hunter has a full mana bar and is up meleing the mob...)

So just wondering if this is normal/accepted practice.