Honestly with the new patch out fastest leveling should occur via questing. I know if you check out joana (for horde) or brian kopps guide (for alliance) they almost stick exclusivly to questing. They have redone their old guide and actually skipped content they previously did because questing gives way more XP now (honestly its in line w/ outlands XP per level).

What i mean by the parenthesis my warrior is gaining % of xp per quest turn in equal to (probably more since 60-61 and after that is a lot more xp per level) what I would gain in the outlands.