Well, that turned out to be easier than I had anticipated. And I'd anticipated it being pretty easy.
There's really not much to report. Blood Furnace is a cakewalk, even easier and quicker to clear than Hellfire Ramparts. The zone is short and linear and there aren't any large groups along the way. A level-appropriate group need only take care in splitting and pulling groups in a couple of areas in order to avoid roamers who can create an aggro chain that would bring an additional group (which would make for a hilariously disastrous wipe... the first time, anyway). The only other concern is the stealthed rogue NPCs who wander short distances and can creep up behind an unwary group and drop a cloth-wearer before anyone realizes what is happening.
Neither of these are a problem for a level 80. You can see the stealthed NPC from a good distance, and can deal with groups without aggroing other groups, even if you fight them where they stand (assuming, of course, that your pet and its current target do not suddenly start the "positioning waltz" across a room). There are relatively few trash groups to clear, and many of the mobs are casters, which means lots of resists thanks to the pet's naturally higher-than-normal resist ratings. This means that he needs almost no heals and I can pull with no downtime aside from my own generally slow pace.
The boss fights are generally straightforward, although Broggok (the second boss) would have been a very real challenge for me to multibox at the appropriate level, since he is part of an event where you deal with four waves of mobs that come in quick succession before you engage the boss. In fact, the boss himself is a pushover, it's getting to him that can be a problem. For a level 80 hunter the only concern is making sure to grab all of the mobs in each wave before they pound a party member into mush. I am using a rhino as a pet, and they have an ability that affects multiple mobs, which makes this event even easier still.
I ran it three times for the group over the weekend. Each run took about 50 minutes from start to finish. If I was concentrating on finishing as quickly as possible, I could probably shave 15-20 minutes from that. Which is pretty good, considering that a full clear is worth about a third of a level for the alts (rested) at level 63. They got through level 62 and are 2/3rds of the way to 64 now. The only downside (and it's not really a downside) is that the loot drops have been a bit underwhelming-- two paladin librams and a few other items that I had to sell (no DE available to the group yet) such as a bow. There have been some upgrades, though. And with the changes to spell power, items that would have otherwise been vendor-fodder are still useful. Broggok drops a trinket that used to have +healing on it, and now has +spell power. So when a second one dropped, the mage or warlock was able to use it.
So... another quick trip or two and they'll be level 64 and at that point my options increase a good bit. I can continue to run BF a few times, or see how it goes in the Slave Pens, or the Underbog, or the Mana Tombs, or the Auchenai Crypts. For a short time I considered doing world quests for some gear and to pick up the quests that direct you to the instanced dungeons, but that would probably take a lot longer than just clearing them repeatedly. So that is my plan for the time being.
During the week I spent a few hours running some of the available daily quests for my hunter, as well as working on tradeskills for him and the shaman. The dailies provide reputation gains that lead to gear upgrades, as well as quite a bit of extra gold. Most dailies provide 13 gold and 23 silver, and you can do most of them in bunches of two or three. Which means that it doesn't take very long to complete ~16 dailies and walk away with more than 200 gold each day. And there are still plenty of normal quests that also provide good cash rewards at level 80 (since the experience reward gets converted to gold). 300 to 600 gold is not out of reach and not as onerous as it would seem. There will be more than enough cash to get the alts their necessary spells and their flying mounts/riding skill at level 70. In time there could even be enough to get each of them their "fast" flying riding skill, though I cringe at the thought of spending 20,000 gold all at once. But the game has made it awfully easy to accumulate gold, while at the same time making it less and less necessary to spend it! This is even more evident for a multiboxer like me-- I have every tradeskill covered by my team, so I can farm the materials and make the items I need, and sell the excess.
My plans remain just a tiny bit murky once the group is 70. With the shaman being an enchanter, she will likely be the healer for the group, leaving the priest out in the cold. But I do intend to do some outdoors questing for the group in Northrend, to help gear them up for instancing, and the priest will be the one who goes along for that. So she will level up with the group and get gear and experience from questing, while the shaman goes on instance runs. This works out in more ways than just being able to DE items. With the priest out of the group, there is less competition for cloth drops. And mail drops (even the DPS ones) would go mostly to the shaman, since the hunter is 80. In the meantime, I plan to work through Outland instances to get the team to 70 and gear them up. If the experience rate holds, it won't take very long to get them to 70.