>>544523804
>>544565390
Also, opening up with Yoshitsune is important for this fight for the Bloodbath Blessing buff, which gives +40% final damage to Wonder for the rest of the battle. You can get the buff using any physical skill if you don't have Yoshitsune.
I also did another run with Lufel, since I just remembered that he should be worse than the cat since Vino already brings burn.
The only other thing I can think of is that your Sepia isn't A6.