Very very RNG heavy. Expect hours of retries if you are underpowered. The hardest part of the fight is when he spews out projectiles. You can i-frame them but whether you get hit or not seems to be completely RNG. I never figured out a way to manipulate it to always miss no matter what I tried. You can do the exact same thing between 2 attempts and in one attempt you'll get wiped in the first volley and the next attempt you'll take zero damage for all 3 volleys. It seems that all you can do is press cover and let Jesus take the wheel.
Even if you get out of the projectile phase alive you still have to deal with more attack cycles and if you don't have any cover left you'll die, so you not only must survive but you also need him not to hit your cover either. That's why in the beginning when he attacks someone, I always make sure they take some HP damage so their cover survives by swapping to them and forcing them to attack for a split second. I got lucky and he whiffed almost every attack in the next phase after the projectiles but if you get here with most characters having full cover then you should still be fine assuming he doesn't target the same character twice in a row, which is the same as the first part of the fight, and Crown's taunt will help survive one or two. Although be careful with her taunt timing as it can come at a bad time where she taunts, gets hit without invincibility, and then the taunt is still active to force the 2nd hit on her, which will kill her and end the attempt. So its probably optimal to try and time it right, but I personally never did as there's just too much else to worry about.