imo its 10x easier leveling a single toon from 70-80 than it is taking a team. I'm currently leveling my DK to 80 (71 right now) and i am having a blast spending 2 hours a day questing in a zone. I have 2 of my 80 shamans follow me and blast everything. I only pick up quests on the DK, and so collection quests and the like are a breeze. I'm actually having fun leveling and reading all the quests and such. I did run nexus yesterday and was able to 3 man it no problem, but for the most part i am skipping instances and just doing quests (going to go back and do heroics at 80 with full team).

In contrast I really did not enjoy at all leveling my team 70-80, even though I mixed in instancing/questing, the collection quests for 2+ people really become a huge drag on fun, and a ton of time wasting as you spend time chasing windows around.

After my DK is 80 and pretty geared I'll probably level a priest next, and again go manual 60-80. I wouldn't go hardcore into leveling multiple teams w/ RAF from 1-60, since I'd guess the next expansion introduces another race/class that starts at 55 or 65. RAF instance leveling from 1-60 though is definitely a good idea, its boring but only takes 24-48 hours and is a nice fast way to have a team at 60 ready to solo level.