When i was leveling my alt, i accepted a Quest named "Kessel's run" its the one where you get the elekk mount at lvl 10 to warn some people near exodar. this quest can be found on bloodmyst isle.
you have 15 min for this quest, what happend i warned the 3 persons, got about 1.3k xp total. and then went AFK, and the quest failed. went back, did it again, and i again got xp for it.
i just repeated this till i got 15 started at 10. boring, but quick xp.
Gl