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.
It's explained in my and @Elebhra's posts above!
To summarize, GWM is vastly superior when you have advantage on an attack, and is generally superior if the enemy AC is low (<12) and your weapon isn't super magically buffed. +10 damage is a lot when basic heavy weapons deal ~10 damage on average, and importantly on a hit, GWM guarantees a high minimum damage (~14) whereas a normal hit can easily do only ~4-6 damage. This makes kills much more likely. Essentially, GWM is high risk, but often higher reward.
