Hey,
you could try one more thing.
From my own experience (experience from my guild, so no it is no official solution!!) , we never kill the boss if one of those three buffs are active on one of our groupmembers (target change, Severing Bomb, Foot Soldier of Perdition)
Since we do this, i can not remember that the barrier has been active after the boss was killed. Maybe you could try this?
Good luck!