some time ago, a chest exploit was posted here. the exploit is to get killed in the same second as the boss so the chest spawnsand the boss despawns.
i found out an easier and a 100% way to get this work, unfortunately only on lower lvl bosses, because you have to one shot them.
what you have to do: get your hearthstone on cooldown or throw it away. now youre at the boss, click auto unstuck and spam any instant spell which will kill the boss. right after the auto unstuck bar, the boss will get killed by your instant and right in the same second you will die. the boss resets and the chest spawns.
i hope it could help anyone and sorry for my bad english :s
edit: maybe try it with http://www.wowhead.com/item=12662 or http://www.wowhead.com/item=20520 ?