My first solo attempt on Ultimate Duke - three deaths, all on Phase Four.

The mechanics of this fight just don't make for a challenging boss battle for a solo player. When everything is targeting you, you know exactly where the attacks will be going and merely need to keep circle kiting. I'm under the impression that this boss fight isn't going live and it is merely to test whether the difficulty setting is manageable... but if the new strata bosses are at the same level of difficulty and simplicity of Duke, then I see them being done deathless solo within 2 days of going live (heck, I might have actually managed it deathless if I wasn't wearing skolver and using a barb thorn shield while fighting him).