ANYONE (stealthed or not, i did it as a mage) can hug the wall and grab the container containing the key, it is on the left side when you look at murmur (his right). It is located on the first ledge, behind a protuding wall, you can see it if you are in front of murmur. When opening the container a elemental will spawn. You can kite him back to the front of murmur and kill him with 2-3 people, without going out of his aggro range. The elemental has 20k hp and hits clothies for about 800-900 regularly.
If you die the mob will return back to his container, the container will disappear, however the mob will not despawn. If you die for some reason or aggro murmur in the process. Just come back in and he will be waiting for you.
Blizzard also nerfed the amount of people that can loot the key at one time, you used to be able to switch out members for others to have a maximum of 2 groups (10 people) loot the key. It is now only possible as of the recent patch that only 5 maximum are allowed to loot it.
GG ALL!