Visceris immune to any damage.

(This is just a copy from a reddit-thread I made)

So a guildmate asked what he could do cause Visceris apparently doesn't take damage from his Glacial Cascade-Totems.
So I offered to help him out and to my surprise, I couldn't damage him either. (Arc Trapper)

Here's a small recording (sorry about the quality, not exactly what you would call a beefy LAPTOP LOL. Also, Bandicam op)
https://www.youtube.com/watch?v=A1tSCdbHyk4

Anyone else encountering issues like that or are we simply not doing it right?
Visceris' buddies are already dead, this is supposed to be his final phase. We even let him go rampant on us without stun-locking him to test if that was the issue.

Also, here's a screenshot of my current damage (it's Cold/Lightning/Chaos), so that shouldn't be the issue either, right?
http://prntscr.com/jx0t1i