Check out Initial Competitive Skill Rating, Decrypted.
If you would, please write down the ranks of people you are playing with/against each game, and your result.
Example:
My team: 2 diamonds, 1 plat. enemy team: 3 diamonds, result: W
My team: 1 master, 2 plat. enemy team: 2 master, result: L
etc.
And let me know how it goes. There have been some rumors that my post is obsolete, so it would be nice to have some fresher data from a high skill player.