Unfortunately, the virtues of the Sixteenth Hall contribute to its problems. It is long, relatively unrewarding, and had the largest penalty for minor mistakes, but it is just as necessary to hit 6/6 radiance as the other Moria end-game instances.
A very good group can finish the Sixteenth Hall in 45 minutes, using “unintended gameplay” that is being removed today. A normal group takes 60 to 90 minutes. So each of the three wings takes 15 to 30 minutes, depending on your group. Except for the last stretch, each features one hell room, one other hard pull, and a series of standard encounters with high hit point enemies. That last stretch is a few big bugs that can be avoided, then a half-dozen queen bugs (with workers) that must all be cleared. The boss fights are not difficult, just lengthy (high hit points) with a lot of disease being tossed around.
The rewards are the worst of the six instances. The first two bosses have nothing of significant value. The final boss yields the shoulder piece token, when defeated on hard mode. The shoulder piece is one of two that are not part of the real radiance set; the Watcher drops that token, and this one is something to tide you over until you defeat the Watcher enough times to win that roll. Beating hard mode does give a 2000 destiny point bonus, if you have the quest; I am unreliably told that this was an accident of programming, as the destiny point bonus was supposed to cycle through the instances, only they could not get the code to work right.
What is hard mode for the Sixteenth Hall? Do not kill the little bugs that swarm around the boss. They have less than 200hp, so pretty much do not hit them, use area effect attacks, or wear any damage reflection gear. If you are a healer, this could be a good time to turn off attack forwarding, so you do not accidentally smack one when healing the tank who is trying to keep the bugs off you. You can still beat hard mode after killing a few bugs, and I am unreliably told that you must avoid killing the original two in the room, while it is fine to kill the rest (mark them or good luck). Who wants to test that theory after an hour in the dungeon? If a first-timer accidentally whacks the wrong bug, congratulations, no one gets the shoulders.
As interesting as this is the first time, remember that everyone in your fellowship wants his shoulders. If you average an hour, that means the average person spends six hours in the Sixteenth Hall, before considering time for finding groups, AFKs, recovering from any wipes, etc. Can you keep a group together for six hours farming the same dungeon? For every person who gets the shoulders on his first try and runs away laughing, someone else is running it eleven times in hopes that this next one is the one.
One of the major reasons I took a five-month break from the game was going 1-for-16 on the 1-in-6 chances in Annuminas. This is the last piece I need, and after a half-dozen runs, I am thinking of just skipping it and hoping to find something else later. There are supposed to be more radiance options in Book Eight (July?), and maybe I can join PUG Watcher raids enough times to win the real shoulders.