that fight was fuck easy.
just set your party AI to attack other enemies. lock on to the boss, blindside him and slash away. Meracles's Comet Impact or whatever, does a bunch of damage and it has a low CP so you can put it on a lot of slots to link it and increase its damage output. you'll kill the boss in like 2 minutes.
Also what's your party right now?
as for skills, no guard(guardless in the JP version)+critical hit are the best for melees.
And if poison is bothering you, anti-poison amulets?
And I've pretty much ignored everything else. I'm going to try to get critical and start maxing that on everyone next I guess.
... wow. is this your first rpg? HP boost is a complete waste of SP. It's not even that useful, considering there are other more useful skills.