Look at the baseline feats for special attacks:
Critical Strike doubles critical threat range but lowers Defense by 5
Flurry gives you another attack at the cost of -4 Defense and Attack
Power Attack gives you +5 damage at -3 to hit. These all seem fairly shitty, but also in-line with each other. Critical might be a bit harsh, especially considering that early-game you're not going to see high threat ranges like mid/lategame, but it's a stepping stone feat anyway. Now look at the Master-level feats for special attacks:
Master Critical Strike quadruples your threat range, but lowers Defense by 5
Master Flurry gives you an extra attack at -1 Def/Atk, practically free
Master Power Attack gives you +10 Damage at -3 to hit
Among these, Flurry/Rapid Shot is easily the most powerful, equating to a full-damage extra attack for a negligable penalty - that's another d12+str, at least. Behind it is Power Attack, whose +10 dmg is comparable to the average d12+str, before bonus damage mods. Critical Strike is terrible; Even on a Crit-focused build where you'd crit on 11-20, that's still not enough to offset the massive -5 penalty to defense, especially in comparison to Power Attack's consistent -3 and Flurry's step from -4 to -1. My question is this - What file do I mod to change Improved Critical Strike and Master Critical Strike's defense penalty?