Character Card System

So the best option for an archer would be:

Card set 1: Mercedes, Wild Hunter & Marksman/Demon Slayer, Paladin, Dark Knight
Card set 2: Mech, Buccaneer & Cannoneer/Jett

Still dont know if its worth getting 3% crit, 3% final attack dmg, 4% cooldown reduction & 1,5% chance for instant death over 4% resistance, w.att thingie from paladin, 4% max hp and 10% hp into attack range. Since both of these are kinda silly bonuses for bowman I think just making a mech+bam+ds together would do more than some silly 3-4% dmg boost on final attack.

I asked this in the maple question section and didnt get a real answer, is the final attack dmg just normal + dmg to what is already there (210%->214% for bm) or is it multiplied? If its not multiplied does mercedes have an advantage here because she have 2 arrows on her fa and it would give double bonuses? or Would it just give half bonus on each arrow/full bonus on one, nothing on the 2nd?

I know it might be 100% waste of time to lvl new chars for the bowman bonus but I want to fill my decks with whats most useful on a mercedes.