So this is a very small sample size, but just wanted to share my initial findings with everyone.
The following is how much xp was gained per minute in each instance. Only elites were focused during the runs.
Nightmare Dungeons - Average 12.5k per minute
Rotting Halls (Ruins of Eridu) - Average 36.5k per minute
PVP Zone - Average 40k per minute
I dunno, maybe I miscalculated somewhere, but that's what I got so far.
