yeah Hinterland is the best for sure.

I liked Ungoro as well, lots of kill quests, lots of 'discover' quests, and a number of very sufferable collection quests that you can do on the way, or buy items on the AH.
WPL i only do the 4 cauldron chain quests, and the torches in andhoral, and in winterspring, i only do the elite beast chain (which is not elite anymore) and the ice giants (those would give me around 600xp a kill, with a 70 in the group)

In earlier levels, i liked Desolace (most people dont) just because of the many kill quests there. and the charred vale harpy quests (including the no longer elite one)