I am all up for hard content like this and honestly i enjoy learning it but does it seem like some of these "One shot" mechanics during the fight can overlap and make it like a half skill half luck type fight?
For instance, i was doing great and then runes spawned, valkyrie's come and i have the other dude going enrage mode chasing me down.. literally no way to do all 3 at once and live. Seems kind of like a cluster of randomness that is not in our control.
That being said it will feel good when i actually do it, even if some luck with mechanics is involved.