How long does it take to get from the entrance to the two chests near the ledge?
If it's under 15 seconds, then would it be possible for someone to use Thottbot World of Warcraft: Invisibility Potion , run to the edge, agro the mobs without dying to the two guards up there (sacrafice void for locks, ice barrier/mana shield for mages, power word: shield for priests, etc) while they run up the stairs, jump down onto the ledge, and bug yourself out of combat.
I know it's a long stretch, but would it be possible?