I've enjoyed having a 70 hunter with a 70 priest. Shield pet, send pet in to round up mobs, misdirect with a volley onto the pet, followed by a nice multishot or some combination of shots.

During the volley there's ample time to send the priest into the fray, to holy nova and re-shield (I use [shift+arrow keys] to move her without moving myself). I personally prefer the 50% damage return on the shields, so it's not just to keep the pet up.

Before the fight I throw down an explosive trap. After the first re-shield, I bring the pet and priest back to me and the trap, where I throw down another lovely explosive trap. I leave them all there as I feign and then get a little range. A few more holy novas fly out from the priest, conserving mana for the final shields and prayers of mending if needed. Interesting to note that the heals and damage from holy nova causes no threat and that prayer of mending adds aggro to the player it gets used on, rather than the healer. And Shadow Word: Death bounces the prayer of mending back off from the healer.

If things start getting hairy then I ensure that the hunter, pet, and priest get at least one mob on them and cast that PoM.. It bounces around 5x and heals everyone for little to no mana. PoM is amazing when everyone is taking a beating. In some areas I ensure that at least one mob is nipping at the heels of the hunter and I can just go around with the pet collecting more mobs, I just kill off the last target the pet had. I stop only to retrace my steps back down the trail of bloody bodies for the loot. Mana and health are always near 90% and it can go on for a very long time. I'd like to know how efficiently other healing classes can sustain that sort of carnage.

I only recently got automated with autohotkey. I had a setup with two machines, but one crapped out, so I turned to tabbing over on the original computer. Actually, I learned to prefer that over having two machines, mouses and keyboards. My script includes key presses accompanied by mouse clicks on the hotbar (plotted in all the x and y coordinates) and shift+arrow keys to move the other pet (I mean my little priest pet). Now that I don't have to tab so much, lots more spells are being sent down range. It's also great that +healing gear is now also +damage gear to an extent.

Priests have shackle undead, mind control and fear, and the hunter has freezing and frost traps for crowd control (sometimes even snakes). However, I'm usually just more interested in quickly getting an enormous group to beat on my pet, which remains shielded, while I juggle aggro with the hunter.

It seems like a lot of doing but it's what I'm used to and I really like it. I've got the same question as the OP, however. I'm experimenting with all the healing classes at the moment, trying to level up each to 70 for playtesting. so far I've got a 55 sham, 46 druid and 44 pally.

To take a break, I just got a couple of druids to level 8 tonight, plan on doing feral and resto. I've always been impressed with what they're capable of. If it's all that I've dreamed I may just get a third account and bring in another druid. Same box should handle it, I got a nice rig =^) Then of course why stop there?

But honestly I don't know the answer to the question, only what I've tried so far. The totems are very helpful from the shaman, namely the agility and earthbind totems, ah, and the mana contributions. The blessings from the Pally are very nice to have, from even a low level Paladin. I can't say that I know what the druid contributes besides healing but the entangling roots outdoors, weak thorns and gift of the wild, so far. As much as I like the shaman, I personally don't like having to lay totems all the damn time though. And having a blessing of kings is mighty nice, but hate refreshing the blessing every ten minutes. Just have to wait til they get a little higher before I can really know what I like the best... So far it's the priest, hands down, for me.