I'll add my contribution now.
The top 1/3 of all participating players are selected.

This type of system, a "BIATHLON-LIKE" one, has already been discussed, but only in the context of offline tournaments. I don't know exactly how it works in biathlon – maybe the number of participants in the tournament is fixed. It has already been said that it's not a good idea to simply take a sports ranking system and apply it to Heroes 4, because it's a computer strategy game. Why did I suggest the "Planets" system? Because it's also a computer strategy game. With your system, where you propose awarding points from the bottom up, and considering that the number of participants in online tournaments is not fixed, it turns out that one tournament has 10 participants, and another has 20. The attendance at the tournament is not the responsibility of the tournament leaders (they have no control over this; it's more of a problem for the organizers).
It's possible that in the first tournament, the leader won 9 games – the maximum – and didn't lose once. And in the second tournament, the leader has eight wins (losing 12 times) – but is this actually possible? :) And yet, they still get 1st place. But according to your system, would THIS leader from the second tournament get a higher rating than the leader from the first tournament?
So, the question is, why would we have such a flaw in the rating calculation? ;)

Added 2 minutes later

To Starhan
Please write the formula... That is, not step by step, but as a formula, just in case your version is the most universal, and your formula needs to be automated... So, give us the formula. :)

Are you kidding? :) There is no formula there. :)