I could be wrong, but I don’t think the win/lose streaks are due to them intentionally making it happen. I believe it’s due to their failure at building a good match maker.
Note that Overwatch has exactly the same issue. One day I get @#$%@$ teammates non stop (e.g. don’t know how to play, can only play a single hero and they aint that good at it, disconnect. toxic,… ), then the next day it’s the other way around and I win even if I don’t do anything.
I suspect they have a job that runs once (or a small number of times) a day, that re-calculate your win rate and based on that decide if you should be skewed toward wins or losses.
Once you combine their poor match making with the fact that your MMR/rank is focused on win/lose and the aim to get those close to 50%, this means that your rank is largely based on who you are teamed with/against and not so much what you actually do, you start to realize that there’s likely more people with the wrong MMR/rank then with the correct one, and therefore the likely hood of predicting a good match is very low. And now you have a vicious cycle that perpetuate the bad.
To add to all that, there’s different ways to play the game, if you mix together aggressive and defensive players, the aggressive one will die a lot more then if their entire team was similarly aggressive since they will find themselves outnumbered in most engagement. So unless the match maker is able to understand what kind of players work well together, and which ones doesn’t, that yet more variable that get into the mix.
I have given up on pvp in this game as the match maker made it just too frustrating. I just have to play brawl once in a while and get matched with a ranged healer which only heal himself and complain that melee assassin die too much to be remembered that this is game is more about who you get on your team then how good you are at it (at least at my skill level).
Finally, Blizzard has done a few tweak near the top of the ladder, but they really don’t give a duck about lower part of the ladder. I wasn’t so far down the bottom when I played this game to notice, but in Overwatch, bronze players often get matched with toxic players (sabotager, non-participation, smurfs, …).
It makes getting out of the bottom to find reasonable teammate very hard for people who are unfortunate enough to be near the bottom.