I personally think CV might actually be worth more than they claim it to be. I know people with the same major, different GPA (3.95 vs 3.6), different CV, but the high GPA person got rejected pre-interview. It's weird because the person with high GPA actually has pretty decent CV as well... not sure why he was rejected. I also know a lot of people getting into McGill with 3.5~3.7 with less difficult majors, which would unlikely happen if GPA + coursework/major difficult = 70% (from last year it was 30% CV/essay, 70% grades).
but...
there was the personal essay part so it may not be a CV thing
also that was from last year so it might not be applicable to this year. if CV is worth 10% this year... even if they secretly make it worth more it'd probably still be insignificant