As a full group in BFD levels 24-26, we were getting 60-90 exp per kill from level 22-26 level elites or so. Walked out of the instance, killed level 22 mobs with 4 people and were getting 50 exp per kill. I can tell you in vanilla WoW days as a holy priest (I was a nub) I leveled up almost solely from instance grinding because I hated solo exp by myself. I don't have any verifiable proof besides "it doesn't seem normal." But has anyone looked into this well? It seems like instance mob exp needs to be adjusted (buffed).
Sorry, when I say "walked out of the instance" I really mean went into Ashenvale and just killed normal mobs, not the elites immediately outside of the instance.