If it makes you feel any better, I had exactly this confusion the first time I went there.
Edit: that south room is the boss room - from there you can go down into that thing that looks like a waterway, and off that is a small room where the shard is found.
Edited by ofSunhold on June 4, 2017 5:25PM
Classes that don't need any class ability nerfs: Nightblades, Dragonknights, Sorcs, Templars, Wardens.