uh... It's barely affect the gaming experience, that when I was reading the combat records, in the page where shows you which companion got most crit hits, the strongest enemy defeated, damage taken...etc.

 

I noticed Durance, for some reason, sent most hits in my team, who mainly do buffs like holy radiance then shoots his pistol, which has a very slow hit rates.

 

While my player character has two more hours in combat, sent 35x hits, Durance had sent 13xx hits out.

 

So uh... does the game count buffs on companions hits? Kinda weird.

All abilities technically 'roll' for accuracy, regardless of what they target or what effects they have. You can confirm this by reading the combat log. It's a bit odd overall but at least it's consistent