"I would consider top 400 still as high level player."
Sadly no.
"We require all the players in the match to be in top 200 for that category. With more players in the match the probability that all of them are from top 200 is much lower. Even though the amount of players in this mode is huge. Not everyone is playing at the same time and I would bet the solo 4v4 players are very often queued together with low rank players - thus their matches does not count."
Indeed. It happens quite often but its good that those games don't count.
Question:
Did you consinder the fact, that a 2at premade team ofen search for 4vs4 and playing it? Does your system get those players then or not?
And a 4AT premade team 200 is WAY WORSER than random 4vs4 top 200 guy. It is ultra easy to get good rank as 4AT premade. You can see in the top 30 4AT premade ladder teams, who have single skill from around 400 or something.
So acutaly it could maybe better to use % instead of a fix number as IntoTheRain suggested. Then you would see that top 200 4AT premade would not count.
On the other side then you would have even less matches in your stats
I think its very hard and probably with the amount of players in coh2 not really working at all.