Interesting.
I beat Purrvis pretty easily yesterday, more or less on a fluke. He didn't kill anybody outright, which helped enormously.
I blew through Corvus' first form and Barburus this morning. I'm gonna give Corus v.2 a shot, but maybe after escaping and saving my game first. Although, honestly, his first form and Barburus were so easy that I'm not really concerned about not being strong enough. Here's why:
Within two turns, I can get my Martial Artist to full Tension with Egg On + Psyche Up. She did 1500 damage to Barburus with Hard Claw using this method. He was dead soon after that. Seriously, as long as Corvus doesn't have like a million HP, I think this is gonna be doable.