Hi, haven't fully tested out what the conditions need to be but after the first boss there are those non-elite firey rock mobs (Slag, thanks to Cheat'R for name) with around 12k hp, once you clear them out, they respawn within 15-20 seconds later, I must say though, after killing the SECOND boss they didn't continue to respawn.. Maybe worth farming, I dinged my char 79-80 rested xp in there, 1200xp per mob (up to 1800 with hierloom).
Not really an 'exploit' but I'm sure it's not meant to be in the game.
P.S It has to be on NORMAL mode (never tried heroic, plus you can't go heroic until level 80 so it'll be pointless.