for 2 boxing, Pallies would be great, but only if all they did was heal. Pallies are probably the strongest and simplest single target healers around, but they have no caster damage output. Your Dk or lock would never die, but they'd pretty much be the only ones working. I guess it just depends what you want out of your healer. I'm currently doing 3 locks and Spriest and it's more than amazing how well that works, I'm barely using the priest's heals (she started out holy) and instead using her as another dps. A pocket healer is a pocket healer, could be a tree for all that it matters, but priests, shamans and even boomkins can respec or switch gear for decent non-melee dps.