i wouldn't say it's THE deciding factor or anything, but the reality is, if you're applying to H/S/W type of schools, most of your competition will have similar if not better gpa with likely a similar gmat as well. i went to a canadian school and suffered a similar fate to you as well...except my gpa was much worse...and i still got into a couple of decent programs.
i recommend considering working for a few yrs before applying. that'll give you a much better chance to get into the top programs. it'll also help you get an idea of what exactly you want to do and hence why you need an mba. also, it'll make the mba experience more relevant and enriching for you...rather than doing it straight out of school. it'll make your profile more appealing to the school as well.
a SVP at my company once said to me that an mba is like a turbo charger or NOS, rather than a jump start. you shouldn't try to use it to kick your career into gear. instead, you should use it when your career is already up to speed and you've figured out why you need one...then it'll really push you forward in your career.