Just look at Man United, Rooney/Berbatov/Tevez aren't necessarily prolific goalscorers, but between them they'll score around 50 goals this year, with another 20+ goals in assists. Throw Ronaldo into the mix with 20+ goals, then the likes of Vidic/Nani/Giggs/Fletcher/Scholes/Carrick/Wellbeck who'll score between 3-8 goals each, and you see why they're competing to win every trophy.
Obviously that's the other end of the spectrum, but if it's the football model for a club like Man United, it should be the model we use too, which I think JC has tried to do with the current squad.
Miller/Mackie/Maguire would hopefully get 30 goals and then 10+ assists, McDonald near double figures, and the likes of Mulgrew/Diamond/Aluko/Smith chipping in with a handful of goals as well, although we should expect a better return from Aluko. Injuries have hampered us this year though unfortunately, which has had an effect on the creative side of our game (see recent games for examples).