Take a good look at this map. Note while there are several more than a single Treasure Chest in Garlaige Citadel, there is only one that appears in its basement.
A basement now full of monsters pumped full of steroids for the sake of Grounds of Valor.
You can imagine my shock when, Chest Key in hand, I saw the Treasure Chest guarded by monsters Incredibly Tough to a level 70 player. Not even a Treasure Coffer! A Treasure Chest.
This is obviously an oversight, and while it's a pretty minor one in the grand scheme of things, I would hope that it would only take a trivial amount of time to fix.