I can confirm now that grimrail 2nd boss is too hard for me at the moment. I just posted a video where I complete the dungeon, but only after Nitrogg bugs out totally.
Beating the fight either the "normal" way, or by doing a burst at the cannon while controlling adds is just very hard without tanks and healers.
Will give it a go again tho when all my 5 chars have legendary ring. Bigger dps is the solution to so many things, and I feel it might be too for the burst strategy of this boss