The Desolate Host Heroic Keeps Resetting

When I start the encounter, everything goes well until I get the boss to 30% health, then The Desolate Host comes out and just sits there. It doesn’t attack me at all and all the adds and the boss despawn. This happens every time. Please fix this and don’t let this be one of those bugs that is still around 2 expansions later. FIX IT

I attempted the encounter a different way by going into the Spirit Realm and killing the other boss. Upon killing her I go back into the Living Realm and the boss despawns but the adds remain. I killed the adds and the boss will not respawn.