Well I did reach the mark of a true uber-1337 mega hax0r gamer: I beat Malenia solo after about 2 hours of attempts. I still think that fight can go choke on a fat one. To me it came down to two words: boring and inconsistent. It's boring for the same reason Maliketh is boring: you spend so much time of the fight dodging her interminable attack chains that I just wanted to scream "***** YOU DONE YET?", and when there is an attack window it's for like 1, maybe 2 attacks, then it's back dodge dodge revolution. In most other fights you can hit trade to some extent, but with Malenia the margin of error is so slim and her damage so massive that it's basically not worth it, not to mention the lifesteal. She can combo her various moves seamlessly into another so it's almost impossible to say for certain if she's going to stop or switch to another combo. The only move that consistently opens up an opportunity is when she slams her sword into the ground, but that's like 20% of the time. So if you want to only capitalize on definite opportunities, the fight's going to be incredibly boring.
But the more frustrating aspect is the inconsistency. There's just no logic, pattern or reason to her AI. The difficulty can differ massively depending on how she happens to feel that particular attempt: sometimes she'll be placid as a sheep, sometimes her aggression is turned up to 11 zillion. And as a result I didn't feel much of a sense of accomplishment from defeating her, I just felt it was 70% down to me getting lucky with her AI. On multiple occasions in the second phase she literally did 3 of her jump up in the air attacks in a row, with zero chance for retaliation in between. So all I could do is just keep dodging and wait for her majesty to grace me with like 1,1 second of downtime where I could heal.
And of course there's still the Waterfowl Dance, which I somewhat managed to not die to consistently, but never found a consistent pattern to dodging it. Again, I feel like I just got lucky, because on my winning attempt I just happened to be far enough away that I could just run away from the first 2 flurries. I still think that move straight up ruins the fight, because it breaks up the otherwise pretty good flow of the fight: you're just constantly dreading "is she gonna do it now? Is she gonna do it now?" And again, there's no logic or consistency to how many times she'll use it, which is a huge factor in the challenge of the fight. Easy solutions could be something like setting a HP threshold where she always uses it after passing said threshold. Or setting a hard cap on how many times she can use it per fight (once for phase 1, twice for phase 2 for example).
So yeah, major poop-ass fight, not fun, not exciting, never doing it again outside of co-op.