Character Card System

I guess the next big question is what combination yields the most damage. This is what I can think of so far;

For Warriors

 Spoiler

Set 1
120 DrK - 4% HP
120 Paladin - 1.5 physical damage
120 Hero - 4% wep def
-Bonuses-
(S rank) +700 HP, +700 MP, +3 ATK, +3 M.ATK, +3% damage to bosses
(3 Advent.) +7 all stats
(3 Warrior) +8% HP to Damage

Set 2
120 DrK - 4% HP
120 Paladin - 1.5 physical damage
120 Hero - 4% wep def
-Bonuses-
(S rank) +700 HP, +700 MP, +3 ATK, +3 M.ATK, +3% damage to bosses
(3 Advent.) +7 all stats
(3 Warrior) +8% HP to Damage

Total;
8% bonus HP
3 physical damage
8% wep def
+1400 HP, +1400 MP, +6 atk, +6% boss
+14 all stats
+16% HP to damage

I imagine this would be the highest yield of damage for warriors. They have high base HP, and you can wash, so they really take advantage of the 16% hp->atk. I'm aware you can replace the hero with whatever other warriors, like DS, but I'll leave that up to each person to decide whether the Adventurer bonus is worth keeping.

If you want a sort of hybrid damage/boss build, you could consider replacing the heros with Demon Slayers in your card sets. Having 8% abnormal resist is so god like, plus you still retain your sexy 16% Hp->Atk thing.

Other physical classes

 Spoiler

Set 1
120 Bucc - 4 damage
120 Thunder Breaker- 2 damage
120 Mechanic - 15% buff duration
-Bonuses-
(S Rank) - +700 HP, +700 MP, +3 ATK, +3 M.ATK, +3% damage to bosses
(3 Pirates) - +6% ignore wep def

Set 2
120 Bucc - 4 damage
120 Thunder Breaker- 2 damage
120 Mechanic - 15% buff duration
-Bonuses-
(S Rank) - +700 HP, +700 MP, +3 ATK, +3 M.ATK, +3% damage to bosses
(3 Pirates) - +6% ignore wep def

Total;
12 damage
30% buff duration
+1400 HP, +1400 MP, +6 atk, +6% boss
+12% ignore wep def

You can replace the mechanic with whatever other pirate you want that would suit your class better, some classes may prefer the extended summon duration. Having a flat 12 modifier is pretty awesome, and free 12% ignore def is great too. As far as I remember, the Rank set bonuses will go into effect based on the majority of your ranks, so having two S-Rank and one A-Rank should still yield the S-Rank bonus. If it doesn't, I'll have to re-think this.

The "I hit cap anyway, I just need help bossing." one;

 Spoiler

Set 1
120 DS - 4% status resist
120 BM - 4% damage taken reduction
120 MERC or MECHANIC (Ill be using Mech for my example) - 15% buff duration
-Bonus-
(S Rank) - +700 HP, +700 MP, +3 ATK, +3 M.ATK, +3% damage to bosses
(3 Resist) - +7 to all stats

Set 2
120 DS - 4% status resist
120 BM - 4% damage taken reduction
120 MERC or MECHANIC (Ill be using Mech for my example) - 15% buff duration
-Bonus-
(S Rank) - +700 HP, +700 MP, +3 ATK, +3 M.ATK, +3% damage to bosses
(3 Resist) - +7 to all stats

Total;
8% status resist
8% damage taken reduction
30% buff duration increase
+1400 HP, +1400 MP, +6 atk, +6% damage to bosses
+14 all stats

The mechanic can be replaced with whatever you want, merc for CDR, or summon duration increase, whatever. I know some classes prefer CDR to buff duration or vice versa, whatever.

All of these were done assuming multiple copies of a specific class. I threw these together just now with some hand waving, no numbers written down yet.

Edit; As far as I remember, the Rank bonus is still decided by the majority rank of your card set. So having a set of S, S, A, should still yield a S bonus. If not, I'll have to re-do these.