In my opinion no one factor is a gauge of skill. You need to take into consideration quite a few numbers to get the big picture. For instance kdr isn't a bad place to start. If someone has a high kdr then I'll next go to recent games to see if they're actually playing. If those numbers aren't something like 10-3, 8-4, 3-4, 12-1, 11-0 I'll look at combat rating and look them up on destiny tracker to get an idea for their true skill in certain playlists as well as the average score per game. That's basically linked to how much they win in and gives an idea of their score for those games. Again you can make a case that each of these stats individually doesn't mean anything, however, putting them all together is a better indication of the players actual skill.