I just haven't been impressed by Samoa Joe yet. His match with Owens sucked, and given that Owens has had great matches with just about everyone, I'm guessing that wasn't on Owens. I also thought his first NXT match (or at least the first one televised on WWE Network) was boring. Maybe he just hasn't shown all he can do yet, but thus far he really hasn't lived up to the insane amount of hype behind him.
Having Owens join the Authority doesn't make much sense to me. You have a guy join the Authority when you want him to be a heel but he needs help to make the crowd hate him. See: Seth Rollins, who isn't all that great on the mic. Owens doesn't need help to generate heat, though. He's an expert at doing that on his own. Hell, he's so good at it that half the time the crowd cheers for him anyway, like when he made fun of Itami's speaking ability and the crowd loved it.
Guys like that should remain solo heels like Lesnar. Owens is more like Lesnar than Seth Rollins. He's proven he can hold his own in a fight and doesn't need to cheat to win. Joining the Authority would just cheapen his character. A guy like Rusev would benefit a lot more from joining the Authority since he'd have people to speak for him. Or Bray Wyatt, since he'd have some guys to help him actually win a match or two.