been a while but I recall the 12-24 game being awful.. 24+ is where it starts getting awesome though, my fav spot forever will be the Iksar Exiles in swamp of no hope (
link), a bit rough at 24 but it's super fast up to 32.
then, if your feeling particularly saucy, you can hop a few zones over at 32 and start doing servants of sythrax and the jesters til 40.
^ one of my biggest gripes with Quarm, is that the exile camp doesn't exist there, unsure if the camp is unique to the titanium client or what.