It's not that you have any weaknesses - it's that there's enough people with stronger resumes than you have (bluer chip resumes and/or more unique achievements), which makes it more likely that you're on the outside looking in.
You need to focus on targeting schools where you have a realistic shot. Trying to "add leadership experiences" as if it were something you can pull off the shelf or just obtain like you would a flat screen TV from Best Buy isn't going to cut it. Most things that are *hard* to achieve aren't resume builders -- they are the culmination of years (or decades) of commitment and experience. You don't become a nationally ranked athlete or an accomplished musician overnight. You can't just assume substantive leadership positions in a nonprofit org AND leave a strong legacy of achievement in these orgs in a year - you have to earn it through years of commitment and conviction.
In short, if you wanted to be more competitive for these top schools, you need a time machine (don't do audit, go to a better undergrad like *ahem* McGill or Queen's or a school in the US, and be less conventional of an Asian).
Again, you have to put your ego aside and focus on schools where you have a shot. Forget about H/S/W unless you are willing to treat them as lottery tickets. Choose 1-2 from Booth, Columbia, Kellogg, Sloan or Tuck - where you may have a shot of getting in, and choose 3-4 from the rest of the top 16 (Haas, Michigan, Duke, Darden, UCLA, Cornell, Yale or NYU) where you will likely find the most love.