How does the point system works?

I am having a big issue with the game. I am a player with diamond on 2v2, 3v3 and 4v4 random games. Every time I go on random game, I will either team up with some players from Silver / Gold / Plat and vs "SILVER TEAM UP PLAYERS" which they themself are diamond in all their leagues. Such game always land me up in FAVOURED position which I totally do not get it. 1). How can random team be on advantage side and 2). even with advantage, HOW CAN IT BE -22 POINTS IF I LOSE? I am seriously pissed with the random point system.

 

http://www.teamliquid.net/forum/viewmessage.php?topic_id=118212

Take a look here, might find what you're looking for.