http://nuggetbridge.com/forums/topic/16118-more-thorough-battle-spot-rankings/#entry200192

Turns out the Pokemon website that shows rankings for Pokemon actually has the official usage numbers hidden in the source code. Which means we can see the official stats for Battlespot Doubles.

>One thing I find interesting about these results is that the top 50 almost exactly matches Scott's VGC15 overview article. Another is that half of all Pokémon used come from a pool of 15 and three-quarters come from a pool of 33.

Total - 2173512 Pokémon over all battles, so taking a Pokemon's usage numbers and dividing it by (2173512 / 6) gives you how often it's used on a team of six.

1. Kangaskhan - 157889 = 43.585%
2. Landorus-T - 137924 = 38.074%
-------------------------------- 10%
3. Sylveon - 86784 = 23.957%
4. Talonflame - 76120 = 21.013%
-------------------------------- 20%
5. Thundurus-I - 72662 = 20.058%
6. Charizard - 69701 = 19.241%
7. Bisharp - 68532 = 18.918%
-------------------------------- 30%
8. Heatran - 66394 = 18.328%
9. Terrakion - 58286 = 16.090%
10. Amoonguss - 58171 = 16.058%
11. Aegislash - 54491 = 15.042%
-------------------------------- 40%
12. Cresselia - 54349 = 15.003%
13. Gengar - 48920 = 13.504%
14. Salamence - 46981 = 12.969%
15. Suicune - 45766 = 12.634%

Here's the top 15, or what makes up 50% of total Pokemon used and their actual usage per team.