I just finished Act 2-2 in Cold Steel 2 and that boss at the end of it the normal party fights gave me fits. Party was Purple Lightning, Emma, Laura, and Alisa. I had Fie, Rean, and the guest character too but I had to permanently bench them for the fight. Laura with Taurus absolutely wrecks everything though. If you can get off 2 s-crafts at 200 cp damn near any boss is dead. A critical came up and I had her s-break and it was a wrap but it took a few fights to line that up.
I'll admit my set up isn't the best. Other than putting Taurus on Laura everyone else has their default master quartz and I've almost never used the overdrive function in the whole game so far.
Rean has the accessory from the Severing Chains (all the people who haven't beat Cold Steel 1 won't know who that is yet) that they gave me for having the highest link rate with them before act 2 started and I put impede 1 and 2 on him. Outside of that not much strategy has gone into anything.