Burton scores 57 goals last season, by my calculations Duffy either got the assist or scored a third of those. That's pretty damn impressive, more than just half a dozen goals and a couple of assists. Furthermore, I feel its fair to suggest Burton weren't overly attacking last season (it worked for you so that's not a criticism), but its not unreasonable to suggest that if you were he would have had more goals and assists, especially when feeding a player such as Sharp.
He wont be the main set-piece taker either, reading Bury fans views on Hussey he will be.
Nobodies expecting a world beater, as you say he wouldn't be in league one if he were. And I'm sure he'll be frustrating at times, dont think I've seen a winger play for us that wasn't. But based on being in the team of the year as voted for by his fellow professionals, he's as good as you can get for L1, better than decent and getting more right than wrong, and that's as much as we can ask.