First of all, thanks for the stats Doug, they're always done very well.
Now, I'd like to point out that Crobat's usage is just plain insane in UU considering that his usages consisted of only 17 days (he was re-added on April 13).
Let's look at what his actual percent should be (or at least an approximation):
*Calcs besides the final percentage are rounded down
30016 battles/30 days = 1000 battles/day
17 days x 1000 battles/day = 17000 battles
(7015 usages/17000 battles)*100 = ~41.26%
Therefore, from these stats, since Crobat was introduced in UU, he has been used in ~41.26% of all battles.
This is probably off by a couple of percentage points give or take, since without the logs, I can't tell how many battles occurred during those 17 days (in fact, a huge chunk of the total battles may have come from this time due to some of the tier switches heightening interest), but this approximation gives at least some idea. However, it's still extremely high nonetheless.
We can do it for Yanmega as well:
(4897 usages/17000 battles)*100 = ~28.81%
That's still really high but again, in reality, it's probably a little lower than that.