A lot of the rather important things have been mentioned already (did we talk about stun immunity? not sure right now...if not: that's your job, too, if applicable to the specific fight). Think of waterlore not only in terms of your direct heals, but also as bursting main healers' effectiveness via the incoming healing buff on your target. This is the real reason why throwing in some waterlore if you can spare the time will generally not go unappreciated.

About the pets:
Quote Originally Posted by Vilan View Post
For pets, usually you'll want the raven for fire mit debuffs. Sometimes I prefer the ghost pet to put a healing mark on the boss. The bear's incoming damage debuff can be handy too.
While this is true, many groups will expect you to rotate pets to keep the fire mit debuff of the raven, the armour debuff of the bear and the ranged crit buff of the bog up at all times as the bare minimum (sometimes miss chances, bear taunts for initial tank support or dead tank substitute, but that's another thing entirely). This obviously only applies to targets with enough hp to be worth the effort, so mainly bosses and side bosses.