My first group, 5 shamans, took 4 days. This included a lot of time working on my setup. I also did a lot of instances with them (well, basically everything before WoW 1.0 endgame).
My second group, 5 mages, took 3 days. Only quests, mostly AOE.
It looks like my third group, 5 hunters, will be a bit faster, but I should still be around 2.5 days.

I am slow