I was trying out the warlock demonic circle bug to go through walls and used it to go through the closed door in the Temple of the Jade Serpent. But when you use it on the door (the door opposite you as soon as the instance begins) it doesn't let you go through it, but instead puts you below the floor of the instance. So you can run directly to the last boss from underground. I guess you could possibly pull the last boss immediately (assuming he doesn't despawn when he leaves his room), without having to kill a single pack, but I didn't test that part because the group kicked me out thinking I was slacking :-)