I found that getting into a good group in MielA down by where the tomb guardians and mummified frogloks gives outstanding xp from 16 to 21 perhaps. Lots of mobs that typically come two or three at a time. Thing is you absolutely need a group because of that. Even at 19, two blues ate my pet in a matter of seconds. I survived only through chaintapping.
Plus the guardians, priests and warriors drop items that can be turned in to an NPC just outside of the entrance to Miel for even more xp and cash.
Truly a good spot.