Consider, though, that it must work this way if every person is to ‘compete’ against 29 oether people. Otherwise, if there happen to be a number of people in any league which isn’t divisible by 30, some people will be in smaller divisions, which actually is not fair as it would probably be easier to win with fewer players.
Let’s imagine that there are 290 people in the top league, including the eventual global leaderboard champion. Each of these people sees 29 other people in their personal bracket. There is a 1 in 10 chance that each of them seeins the global leaderboard #1 in their bracket (29/290), so we should expect that 29 people will have the global #1 in their bracket, and will have no chance to gain the top rewards.
This works out, I think, on average. If there are more people, the chance of the global #1 being in any given persons bracket is lowered, so he or she will still only deny 29 people (on average) any chance of the top reward. That is exactly what would happen if we were all grouped into ladders where we had 100% mutually shared the same group of opponents to compete against. So I don’t see this situation as a problem.
The problem is that the relegation, promotion, and rewards don’t work – for whatever reason – based on your standing relative to the people you are told you are competing against.