Priest + 4 mages, questing
So far it's been a mixed bag, but with a lot more good than bad. The group is level 31, almost 32. I plan to level them to 80 via outdoor quests, and then... I don't know. I do plan to level their alchemy and jewelcrafting to max at some point as well.
The good
It's an AoE fest with this group- I can use Flamestrike and Blizzard if I want, but mostly I just use Arcane Explosion, and occasionally Blast Wave for kicks. The priest has Holy Nova and Power Word: Shield, which means that I can round up a few mobs without worrying about her health (or that of the mages, after the first AE).
Also, single-target DPS is very high. Four Fireballs will typically obliterate anything of even levels. Anything that survives can be wanded down, assuming that the fire DoTs don't finish it first. For elites, there is Pyroblast, which takes a while to cast but is a great opener against high-HP targets.
And of course, free food, free drink, and eventually free ports.
The bad
So far, dealing with mobs that are 4+ levels above them is a royal pain in the ass. This is decidedly different from the group of hunters that I had leveled up some time back. I think their record was 10 or 11 levels (I recall that they easily killed a level 25 named storm lizard in the Barrens at level 15). Every now and then I am in an area killing mobs that are +2 or +3 levels, and suddenly I get one that takes very little damage and it turns out to be a +5 or +6 and I have to run or die.
Other than that, it's pretty much a cakewalk, and I am even enjoying collection quests in areas where I can gather 3-6 mobs or more. I guess at some point the novelty may wear off, but only if I don't find enough good AE spots as I level.
I'm spec'ing them fire at the moment, since it provides good range and good single-target DPS. Blast Wave is nice, but so far is really just a gimmick. I'm wondering if I might be better off spec'ing them as frost. Frostbolt doesn't do as much damage as Fireball, but it seems to use much less mana. Not that mana is much of an issue with this group...