Larian Studios Forums Divinity: Original Sin 2 Divinity - Original Sin 2 - General Finished a solo run as Archer + Feedbacks

One Man Army should work like this:

You get the boost as long as you are the only party member in that combat. If another party member joins, you lose the benefit immediately. No more futzing around or figuring out the difference between Companions and human-controlled players. It's called "One Man Army", so it should only work if you are the only one in the fight.