Character Card System

This is something minor, but you made a typo for Angelic buster. Should be buster instead of blessing xP.
Anyway, Kanna's card effect adds 1/2/3/4% boss damage and Hayato's card adds 2/4/6/8% minimum critical damage.
Seeing as how we'll probably get Demon Avenger (whose character card also gives boss damage) along with the other classes in the near future, think the effects from that and Kanna's card stack with each other?

I have a Merc as a main and thinking of submaining a revamped Wind Archer in the future. So I'm wondering if these sets would work?

[Set1]
Marksman (4% critical rate)
Mercedes (5% cooldown)
Wild Hunter / Wind Archer (instant kill /accuracy boost or filler)

3 archers for +3/4% damage to final attack skills. If I'm able to get the Wind Archer to Lv200, then I can use the rank SS effect.

[Set2]
Aran (70% Chance of healing of 6% HP)
Demon Slayer (3% Status resistance)
Hayato (6% minimum critical damage)

3 warriors for 8% HP to damage.

[Set3]
Battle Mage (4% damage reduction)
Xenon (+20 Str, Dex, Luk)
Demon Avenger (+3% boss damage)

Resistance set effect for +7 stats.

The only set thats worth aiming for in terms of damage is the pirate set, everything else should be ignored (especially thief, magican & warrior ones). The archer set is pretty terrible aswell, 4% more damage on final attack would mean 8% more damage for a merc. Now this is chance based so it will be knocked down to 5.6%, thats not worth keeping bm, wild hunter or wind archer for, hell even marksman card is kinda pomegranatety for damage increase.

Do as [MENTION=5338]LiquidSwing[/MENTION] said but replace marksman & 3rd archer with kanna + aran, at least for bosses that have potion cooldown. 4% crit chance wont make a big difference at all, my merc is sitting on 95% crit chance with lvl 1 link and decent se alone, if you got a wind archer/wild hunter/adventurer bowman in party you'll hit 100% so easily. If Im not mistaken, just kanna card alone + S set is better than SS set + 4% crit from marksman, unless you REALLY want that 300 hp difference so badly.

You could also replace mercedes card with something better in the future, its not that needed, I only find it handy for mikhail link and ab link skills.