Last night we had one person drop off at the last boss for the weekly heroic strike on the moon. We had to improvise and found a real easy method of killing the boss, by exploiting the room. It just takes some repetitive grinding to bring boss down, but effective nonetheless.
Just do damage at him from the room you start the last boss encounter in. Eventually the room will spawn a chandelier (shire?) with some wizards...etc. When that happens run towards the back of the room where you first started and exit it. Hang around just outside of it, waiting till the enemies and the chandelier thing dissappears. Once they do, just rush back to the entrance of the section and give everything you got on the boss. Rinse and repeat until the boss is dead, which will finish the mission.