Well, it seems to have got much easier now. I had a fight against the Cardinal (or rather, a demon-fused version of the Cardinal) which was alarmingly easy. He cast Doom on three of my characters, but since I killed him in just two hits (my White Mage’s “Holy” spell did over 300 damage!) that wasn’t a problem.
He was a sort of end-of-chapter boss, as I’m now onto Chapter 3, and am about 20 hours into the game. Of course, I’ve spent nearer 25 so far as I had so many failures (mainly on the hangman’s noose level) and retries that don’t count towards that time.
I’ve started swapping some jobs around too, with my White Mage becoming a Mystic, and my Squire becoming a Knight. I have a Monk too, but she’s useless.