Thought so! ... Sometimes, the Current Final Boss doesn't go to his second phase right:
Spoiler
Burns are annoying. I can usually get past the first phase no matter how I do it. ... Mythril Robe is great!
Spoilers
That is, he stays dead and only is revived later, by Green Midboss, to ~100 HP.
Might actually not use any of the top floor gear, and go with a slight, healy variant of my Midboss-beater set.