No offense but it seems like you're playing this like a dark souls boss, running is better than rolling around (unless you got evade extender) and even then you should do superman dive if you know you can't avoid an attack as that one has a longer lasting invincibility frames You should also unlock other mantles as the other ones actually has combat effectiveness Also theres like a lot of downtime, especially in the 2nd phase, where you just don't attack despite the openings making the fight longer than it should be
You're probably right about playing it like dark souls, guess I'm too used to that genre of games. Thanks for the tips I'll try to incorporate them into my gameplay!