The end of the leaderboard is horribly bugged. Looking at the leaderboard, the last three places on NA are 1528, 1519, 1514. I have 1526 and am not on the leaderboard. The reason, once someone is knocked off the leaderboard they have to play a game to get back on. This isn't decay, it is a bug. The first one to play a game gets back on the board, even though there is a gap to the next spot. If you scroll up the list, there is no gaps like this at all, just at the end, and a little at the top.