Different types of buffs and debuffs stack. So if you have two people who have a A type(also called frame) debuff, only one can use it. But you can stack A and B and C.

-40% Def is something you should aim for whenever possible. The easiest way to get this is to use Gawain (Ambush, -20% Def A frame) or Dartagnan (Sniper Shot, -20% Atk -20% Def B frame). Set either Sniper Shot or Ambush as EX skills and your Soul can get you -40% Def on the boss, increasing the damage your party does by a ton.

For the record, if you want the enemy to do less damage to you, Joan has a -20% Atk A frame debuff. So you can combine that, Sniper Shot and Sol's -20% atk C frame for a whopping -60% damage done to you. It's up to you do you want -40% Atk -40% Def or -60% Atk -20% Def.


Sol's first skill heals, and then removes a debuff from your party. It's a problem against Zombify, but that debuff doesn't happen much I think. If you're worried about Zombify, you can always bring a Vivian's cleanse as EX skill.