You have to be strategic. You don't need to improvee your GPA for McGill, but it would help. If you're also applying to other schools, your GPA is likely too low. A master's degree rarely helps you get into med, and when it does, it is only marginal.
That being said, depending on what specialty you're into and its leveel of competitiveness, it can sometimes be helpful to have a grad degree, but that's another story...