In Bosh's 4th season, his per 36 mpg numbers were 21.1 ppg on 14.8 shots per game.
In Bargnani's 4th season, his per 36 mpg numbers were 17.7 ppg on 14.7 shots per game.
In their fourth seasons, both player were taking virtually the same number of shots per minute. Bosh played 3 more minutes per game than Bargnani.
The problem with saying that Bargnani would get Bosh's touches is that Bargnani simply can't create a shot like Bosh can. Simply giving him the ball more doesn't mean he's going to score more. It may mean he takes more contested shots and shoots with even less efficiency than he does now. When Bosh was out this past season, Bargnani's shot attempts actually went down, in part because Bosh was not there attracting the defense, and in part because the teams best big defender could focus on Bargnani. Bargnani needs better scorers around him to create scoring opportunities for him.