I don't think it's vital for Duchene playing with O'Reilly to have success as it is for O'Reilly playing with Duchene.
Duchene is the type of player who makes other players around him better, something I never thought I would say after his first 3 seasons since he looked like an individual "do-it-myself" player, but his game has changed a lot and it's for the better. No doubt he and O'Reilly have great chemistry together but so does the Tanguay-Duchene-Iginla line. Why break that up? So that we can hopefully have an O'Reilly-Duchene-Iginla line that has chemistry? What happens if O'Reilly can't mesh with Iginla? We ruin the one line that actually has chemistry just to see if O'Reilly can get his game on track? Absolutely not
Fact is, salary does matter in this cap era. And a player making 6 million per season is not going to be given the benefit of the doubt just because he isn't playing with our best player. As one poster said, he's playing with 2 of the last 3 calder winners, there is talent on the line, more-so than our first line for crying out loud. The problem that I see? They just aren't working hard enough, simple as that. Duchene, Iginla and Tanguay are all working their tails off every shift and it shows, they're actually creating chances. The 2nd line? To me it looks like they coast when they don't have the puck and aren't going to the gritty areas to score goals.
All three of those players are struggling, MacKinnon more than the other two but there is enough talent there where they shouldn't be this bad. And if they still can't figure it out, then tinker with the 2nd and 3rd lines. Do not wreck the one line that has chemistry on this team for the sake of O'Reilly