My final setup for the end boss was: Vahn, Oalson, Jasmine and redmage. Vahn and jas were doing 25-30k dmg per turn while Oalson about 50k. Beef up Oalson with tabs and you'll be fine.
Super solid squad. Oalson for me was too squishy for most fights which was kept him out of my main squad. I did get to revisit him after I got his magic stat and yeah he was doing 25k easily. Very strong character and I'd probably mess around with him more in another playthrough.
