Man, I think the last boss is rather poorly designed.
They create an artificial difficulty by removing your focus, unlike Sekiro which gave you all the tools to use.
For all other bosses, I can get a Raining Strike, focus a sweep, pummel, and another Raining Strike when they stand up, speeding up the process.
Fancy moves doesn't seem to be working too, he weaved all my Raining Strikes, and all i can get is a light, light, heavy. I really wanna see someone do a fancy move on Yang. Maybe a backhand strike will work, but I'm not that skilled yet.