Stop farming. At best do it once per week per char, even if it should be featured dungeon. I´m on run 68 this way now, still no drop. Can´t count the bugs this dungeon has. Catalyst questline is also bugged, but you can get the requirements for the catty finished in the jorunal before the weapon drops or the questline is finished. But whats interesting for me, did you manage to get the exo from sundered doctrine?