Moons of Peril is the most tilting boss content I've ever done, on account of the invulnerable phases
I can't think of any other bossing content in the game (besides bloat, I guess) where you can get the boss down below 10 HP and then have to wait another 30 seconds just to be able to do another auto attack and finish it off. I think MoP would be infinitely more enjoyable if we actually had a way to deal damage during all 6 of the intermediate phases, instead of just clone phase (which is still broken btw, I just hit 13 0s with a godsword at max combat, please fix).
The frustration is amplified by the feeling that some of these phases aren't even worth interacting with. If you get blue moon to sub-100 HP before the brazier phase, it's not worth leaving the middle because you already know you'll finish her off before the next phase starts. Then you've got blood jaguars, where for whatever reason you stop receiving additional healing halfway through, so why do I even need to keep attacking??
Jaguars are a glaringly obvious case where attacking the jaguars could damage the boss, which would make it feel worthwhile. During the shield phase, the boss should take damage from its own attacks recoiling. During the weapons phase, hitting the glacier should damage blue moon. Lighting the braziers could deal damage to blue moon instead of simply stopping healing. And during the blood pool phase, why couldn't the boss stay there to continue being attacked while you dodge the pools?
Obviously if such changes were implemented it would make the content faster, but that could be compensated if necessary by giving the bosses slightly larger health pools. It really would make the content so much more enjoyable than it currently is, where my primary feeling is anticipation, hoping I don't noodle when the boss is almost finished off so I don't get stuck for another 30 seconds, followed by frustration when exactly that happens. It's a huge shame too, because Neypotzli is visually stunning, and the self-sufficient gameplay loop where you can just camp there for hours is excellent. I want to love grinding this content, and I hate that I don't due to how the mechanics currently operate.