Ok, so tonight I was leveling up my friends paladin, and I had this quest "That's Abomible" or something, in icecrown
At this spot- there is a ton of mobs, I gathered them up and clicked on the summon thing but I forgot to get the mats, so I had about 50 mobs to kill. When I killed them, I noticed they gave full xp, and 5 second respawns. I used Seal of Light and Judgement of light + pots and bubble to stay up, gaining about 40k xp per min, so try it out and level up!