My desire when doing my multibox groups has been to have enough passive healing while DPSing to survive instances. So far, the clerics and bards have been the only fully successful groups at this, though the bards are the only ones that reliably survive the final encounters of zone invasions. My cleric group can heal passively enough to keep my justicar tank alive but there isn't enough group passive healing to keep the other 4 alive. I'll admit I haven't tried inquisitor builds because they seemed too squishy. I may have to retry them with a different spec and see how it goes.

The other consideration is extended battles. My clerics were having mana issues, though I think a split spec where I had two of the mana regen abilities would probably solve much of that. My bards have zero issues with mana, even moreso once one of them got the -12% ability cost aura.