Well today I finally found it after very, very many runs but when I entered the dungeon I didn't get any credit for the achievement. When I checked my achievement tab, Tomb of Sardar and Musings of Sardar were both still unchecked. I cleared the whole dungeon, entered out and in several times, but nothing seemed to work. I was really happy to finally find it, but now pretty disappointed for it being in vain. Has anyone else experienced this?
Here is a screenshot of me being in the dungeon, and the achievement still unchecked.