Hey,
Here is my point, I played all my ranked match with a friend, after our 10 placement matchs, I was plat and he was silver, that was the 1st surprise !
And now, in every game, I’m having from 1 to 11 more points than him. For example, yesterday in a game with 9 diamond and 1 gold (my friend), I had 200 + 11 points, and he only got 200, as he’s gold playing with diamonds, why dont he got more points ?
I really don’t get how it works…
There is a hidden number that determines your personal rank adjustment
If it’s high and you played in a Rank that’s lower than what the system thinks you should be then you will get positive personal rank adjustment points
And points are deducted if the opposite happens
This number rises or falls a great deal when you win or lose multiple matches in a row
That +11 = PRA
Basically HotS has two systems in place in ranked. Your visible rank and your hidden mmr. Mmr is the real measure of your skill level and is affected by many many things, like the mmr of the other players in the match, your win %, how many games in a row you have won/lost, lots of complicated things that we won’t really ever exactly know for ourselves. Your rank is an outward facing representation of your skill to showcase a ladder and make it feel more like a game so to speak. Because rank isn’t affected by all of these other factors, PRA exists to bring parity between a player’s rank and their mmr. If your mmr is much higher than your rank for some reason, your PRA will go up. If your mmr is lower than your rank, you get a negative PRA.
Reply By = Reddit User = secret3332
Hope that answers you 
And next season, the MMR will be visible which will make things more clear for you
The problem is that if you have negative wr and start to get more wins than loses and your rank start to rise, you seem to get points faster than mmr and your rank will have negative personal rank adjustment to slow down your progress.
If you have old account this adjustment stays very long time (mmr will rise slowly) some kind of anchor mmr.