>>533911841
It's hard to say since Grym and the Inquisitor are completely optional. So is Ethel, and the githyanki patrol, which are the other boss-like encounters in act 1. Hell, even the goblin fort leaders are optional, otherwise one could say Ragzlin and Minthara and Gut are the act 1 bosses.
Act 1 really doesn't have a traditional boss since everything is optional, so Grym and W'wargaz are the best closest answers.