I played the 3ds version and I recall that boss fight. Sigh. I think I played it on easy mode just to get it over with.
I'm not generally one to pick at things like frame rate issues, I'm not overly "tech savvy" when it comes to things like that, although I'm trying to learn. While I wouldn't consider myself a pro gamer, I'm also not shit at games and can account for things like lag once I get momentum going.
LOS1 was heckled and dissected for frame rate issues and I can honestly say I never experienced ANY.(The only time I noticed any frame drops were directly after command grabs)
MOF was another story, and this boss was the worst of the worst of examples. However, the fact stands that taking any hit from this boss was like watching AVGN lose at the original Street Fighter, once he'd hit you once, you'd just get flogged like you were in the stocks and there were frames of animation missing noticeably.
I myself refused to tone the difficulty down, so I made the conscious effort to backdash pre-empting every attack, because it was the one place where the game's framerate was broken. I have to say that the rest of the game was actually playable, though some areas displayed shittier framerates than others.