I have 6 characters to max out, and I'll probably do it via questing and doing each dungeon once for most of them. At the moment, 90-100 with SoO LFR gear will take you around 10-12 hours, depending on how much time you take out to play with garrison, followers, etc. along the way.
It isn't. You're bunched in with other players along the way, although they might finally switch on that reverse-CRZ mechanic (too many players in one zone = players are divided out onto different realms).
However, the one vehicle quest there is places you in a solo 'instance' (ie. you don't see others and them shooting doesn't affect you), so at least we won't have the MoP intro farce again...