I have ran duality 11 times now and haven't had a single Unforgiven smg drop. Another friend who never completed the dungeon prior to the Monument of Triumph update has completed it around 7 times and hasn't had it drop either. A 3rd friend has done a few runs and has gotten them to drop but he had it in his collections prior to the MoT update. It might be bugged like the iron banner gear was to where you can't get it unless you had it prior to the update.