The chest is often at the end of the instance behind the Archaeologist Don Laborm. My suggestion is you start by clearing a path to him (Generally that will get you the updates for everything but kill the captains (Which spawn adds through out the fight, the spawn location is where the mob is pulled from so you want to make sure to pull any possible undead adds that will add when adds are pathing. I dont remember if captains lock hit points on this one till the add is dead).
You get the key which will save you killing a ton of adds from the red mobs that are on the rafters by Don Laborm. I would suggest you get the key, if you die in certain cases those mobs will agro from anywhere in the zone making a wipe tough to recover from.