Because I tank for the guilds I'm a part of, I feel obliged to get my tanks to 80 as fast as I can, which depending on how the game changes between now and the release of the expansion will probably mean respeccing to a DPS mode to make things easier. (I'd prefer to sit back and see the content, but I feel like I'm obliged to be ready for raiding as soon as I can be.) Similarly, both of my shamans will probably go enhancement, possibly speccing resto if enough people are on to run the new dungeons. I don't expect to roll in as much gold doing dailies once we're in expansion territory, so I'm trying to ensure I have enough gold stockpiled to respec at will to tank or heal instance runs and still go back to DPS mode for grinding quests.
Essentially, I'm busy making plans to manage getting four 70's to 80 as fast as possible. I know the first one I start will be at a disadvantage, as the others will all get rested XP, but I'm expecting to rotate between them to take the most advantage of rested I can. So, I ask you: what other suggestions do you have for me? What should I do to maximize my leveling productivity? Do you recommend instances over questing? Should I instead focus on one character at a time or rotate them? How did you make the jump to 70 and how are you planning to get to 80, fast or leisurely?