For some degree it can be explained by the mismatch in matchmaking, which now is fixed.
If this guy is true, he just lose 2 points if he lose a game. Good luck for players with a skewed rating to get back to there real rating if they only loose 2 points each game. If he wins, he wil get 19 points. This is quiet strange to me and makes me things something else is wrong too.
You can easily set the average back to 1000, but is this really a solution to the problem? If there is something odd in the calculation the average will still continues to rise again, so after 6 months, ratings will still inflate. Also the skewness will still exists.
I think the first step will be finding the root of the issue. Then we can have a look at how to fix this.
If we want a good working matchmaking for team games, than we need a good Elo calculation.