If Gallagher played with guys like McDavid or Crosby maybe but then we'd probably be having this same argument regarding Gallagher. Gally, like Danault, is not super high skill. He's basically the ultimate grinder.
Ideally though, I agree that Danault is better suited to the 3rd line. He's doing a good job all things considered right now but Id rather him be our version of Jordan Staal. A guy who can play against top quality opposition and frustrate them or a guy who can be used to exploit lesser opposition if the other team avoids the matchup