I just completed my first solo Duality dungeon run and was expecting to receive the triumph; however, this did not happen. I had to do the dungeon over the course of two days and went to the Helm occasionally to clear out my postmaster. In order to get the triumph, are you not allowed to leave the activity? If so, it is not indicated anywhere that that is the case. You can review my play history on my Hunter and see that duality was the only thing I played, and I did it alone. I'm not expecting the flawless triumph since I died many times trying to complete this.