As has been pointed out, the PPG isn't so different to Gannons PPG. Given Gannon had a full pre-season and Rusk has had 2 games with incorrect red cards, I actually think Rusk is doing just as well as Gannon was.
You weren't questioning Gannon for 27 points from 15 games.
Rusk gets the rest of the season. Finish outside the playoffs, he should go. Otherwise, he stays.