i don't see why GWM is good. -5 attack is a big hefty penalty to me. that's like what? 10 strength/dex to get +5 attack for what? 10 damage? yeap +10 damage does sounds nice but only when you have super high attack and the enemies we are fighting are rats? even with advantage it may be tough to roll a good dice. not quite sure with a physical dice but in solasta even with advantage the miss chance are pretty high.
