LANGUAGE WARNING IN THE CLIP: There was a bunch of weird stuff happening, an invincible tank taking non-stop damage from my witherhoard (I've had this happen in normal Vox Obscura solo as well), the constant damage even proceeded into the boss room, where I could see the damage ticks on the tank through the wall. Some other very severe server issues where I couldn't stun the champions, and where my fireteam saw my hundreds of meters away when I was right next to them, so this may just boil down to insanely poor server performance. I was there for the mission start, I didn't join it in progress.