I admit I must not have been paying any attention to the group's experience levels when I left them off before I took my break. Or maybe I just figured I'd get them their level "next time." As it turns out, both the paladin and the mage were in the same boat as the warlock... a single experience point short of level 62. The priest was around 500 experience points short. In other words, the group had been a single kill from level 62 for more than two months! That was quickly rectified, then it was time to pick up where I'd left off... kinda.
The hunter is now level 80, and his stats are more than enough to deal with level 60 instanced zones. He has around 14,000 health, 7,600 mana, ~2,750 attack power, and his pet's health ranges from 8,800 to 10,200 depending on which pet I have out (the former being a level 75 cat, the latter a level 79 rhino). This is considered under-geared for the new expansion, as it seems typical for a moderately-geared hunter (ie, pre-raid gear) to have around 17,000 health and 10,000 mana. My goal with the hunter is to continue to quest with him to build up his gold (currently just under 1,100 gold, mostly due to having purchased all of his flying skills during the leveling-up period) and work on daily quests to get his gear upgrades via reputation items. But I will also be working the multiboxed team as well, looking for quests that help them get some easy rewards, as well as continuing to get them through instanced zones for most of their exp and gear.
With the hunter at 80, it makes the early Outland instances a breeze, and I decided it was time to finish up Hellfire Ramparts (see my post below on how that had gone, to date). Watchkeeper Gargolmar was an easy kill, and Omor the Unscarred was just as trivial. Vazruden and Nazan went down quickly as well, though I lost the rest of the group because I wasn't moving/healing quickly enough (actually, I was healing quickly enough, but Vazruden decided to put an end to that by quickly dispatching the priest. The rest of the group succumbed to the fireballs from Nazan). I got the group rezzed and back in time to get their final quest item and complete the "Weaken the Ramparts" quest. It's a cheap victory, but I want to get through Outland as quickly as I can, and at my pace that is going to take a while even with a level 80 hunter leading the way.
As for the priest/shaman question, for the time being I will level the priest with the group and continue to level the shaman on her own. I'm still not sure what I'll do once I'm ready for Northrend instances, though I may go with the shaman out of convenience. She'll be 80, which will make the group a bit lopsided at first (running sub-80 instances with two level 80s) but she is my only enchanter and so she'll probably be a lot more useful in instances over the long run, at least from that perspective. But it's still a bridge that I don't have to cross for a while.
Next up is the Blood Furnace! We'll see how it goes...