Yeah, I pretty much have cleared everything on DD CS except for Quell[a] and Nageki[a].
For reference, on Kaiden I end Quell[a] with 22% life. After that is Nageki[a] and I fail it when those alternating chords appear.
I guess it's time to use Training Mode to "study". Maybe I can find a way to mash those chords.
What's not helping is that there is a vid of a guy clearing Kaiden on a Dualshock controller. That stuff is incredible.