In 3v3 and 4v4 there are tons of players who are terrible (like 45% wr) but have one or two bloated 50-150 ranks because they grind or get carried a lot. Odds are that they do terrible in other modes or with other factions. I hope those wouldn't influence the stats too much.
(3v3 experience)
Not necessarily. When I started playing competitive, I had 13 wins in a row. Started at rank about 150. Then I had another 3 or something wins in a row of games I didn't even play because somebody DCed on enemy team. Got to rank 100something. Then I had about 10 loses in a row. A couple of DC, flaming teammates and just bad games from either my part or we played badly as a team. Loses but good games if you know what I mean. After that I oscillated between 100 and 300. Got to top 20 on a couple of occasions, even won vs top 10 players, but again dropped to mid 100s. Rinse and repeat for past year and now I'm stuck at 100. Rank 1500+ really do have trouble dealing with MG42s or pak howis or mortar encampment. But TBH, I haven't encountered a lot of players in top 400 that don't know what to do. Most of the time it was just bad decisions at the worst of times that cost you the tank or two and kaput. That or picking commanders that do not have a response to an enemy build (most of the times it was no offmap for lefh spammer).
My biggest success in COH2, being a casual player, was that top 20 position. Winrate? 52%
Were there games that I got carried? Sure
Were there games where I carried? Sure
I would drop the "tons" adjective. Because in top 200, that would mean around 150 are getting carried.... By whom? Who is carrying those people? In a 3v3 game, who is constantly carrying those people? And furthermore, if they are getting carried, it must be from some top 50 or sth player. Where are all those top 50 players? Also, the MM is designed so that the ranks are always averaged against the teams. If there is a top 50 player on your team, that means there is a top 50 player on the enemy team as well, or even better.
Next, it's a 3v3 game. If you have such a big liability in your team (the person getting carried), then you really have to carry the s*** out of the game to win. Because a liability in 3v3 means a lot of veterancy for the enemy and not a lot of damage from your team.
And lastly. These are random 3v3 games. Can you say with utter certainty that the person you PNGed is really a bad player? 50% winrate is pretty much the definition of "you lose some, you win some". In a game of 6 or 8 RANDOM people that's hell of a winrate. Especially considering the fact that if you drop to rank 600+, you're going to have a hell of a time getting to rank 500. Constantly getting paired with flamers, kids or people that have 2 left legs for arms.