fighting the rogue

I know I'm tedious
I've read being at level 18-20 is ok to defeat him (I'll check) problem is characters die fast and I've just 3 mandragore. What's not convenient.. I've Karine's weapon found at rogue's territory that hits 300 with boost.. but she counter-hits that's why she dies often.. I can't change her reaction, or if I try changing the weapon.. but she'll hit less.
Advices?

Advices?