GAC, in its current form awards your ability to hit as many targets in the scoring system as possible (see feats). The leaderboard's point is to highlight those that not only managed to win as many battles as possible, but also managed to do so efficiently, while also taking an alternative path from frequently used teams to complete the character specific feats, and in that aspect the scoring system is fine.
There should not be a higher importance given to simply winning (or even getting holds on defense for that matter). However, as pointed out over and over, divisions need to be extended. There are multiple feats that are arguably much easier to achieve in the lower end of a division than towards the higher GP brackets (especially in division 1). Some people just need to plug in the 1-3 feat specific characters in a solo team of theirs (like Wampa vs weak Phoenix) while others need to straight up lose a battle on purpose. In that sense, leaderboards are disingenuous in their current form (but could be more accurate with more divisions).