Recently me and 4 RL mates was doing PoS, and right before Forgemaster Garfrost I ran ahead as a hunter and missdirected the boss to him. He and the others were still fighting infront of the stairs, so Garfrost ran down there.
The "exploit" is, that when he jumps back to forge mace, you will be so far from him, that the debuffs will disappear automaticly, meaning you don't have to hide behind the rock.
Please no flame, it's just a hint, and I'm calling this an exploit because it's not intended, that the debuffs should disappear by itself.