My sister finished this chapter just before I was about to start it and I just spent the whole four hours asking her when it would be over...
Edit: I think one of the worst parts of this chapter was that you gained NO EXPERIENCE for defeating enemies!
As for the ring, it's easy to defeat the MT if you just HOLD square (on PS4, not sure what it is on XBox) as they're about to hit you. Your MP does get drained faster, but you're guaranteed to hit them every time. I always pressed square too early, so the spell missed, but if I start holding it down when the MT starts to swing their weapon and only let go after they finish their attack, the Holy spell hits every time. I have my sister to thank for that hint!
Hope that works for everyone else!