Character Card System

[Set 1] Mechanic, Buccaneer, & Thunder Breaker.
Effects; Buff duration increase, level to physical+magical damage x 2, Ignore Monster defense

[Set 2] Demon Slayer, Dark Knight, & Paladin.
Effects; Status Resistance, max hp and level to physical damage, hp to damage.

Except for maybe Kaiser in one of the Warrior Slots, does this Card set up seem viable and optimum or is there a better option set up for a Mercedes or Dual Blade/Shadower as the main target for these effects.

First of all, I dont think its worth spending so much time into this and many char slots but be my guest if you want to. However I still think you should move away from thunder breaker and get angelic burster instead and replace dark knight with kaiser.

If I were you I would go with

1st set: Mikhail, Kaiser & Demon slayer
2nd set: Cannoneer, Angelic burster & mechanic

But no the kaiser card is horrible for mercedes, dual blader and shadower simply because you dont need 2ndary stat after tempest but he still gives the 10% link skill rather than like 4-5% from dark knight card.