Unless Blizzard has some kind of crazy AI, this is a mental bias (confirmation bias? I forget the exact term) that happens in almost every MOBA or competitive game.
Think about it. What are the odds that Blizzard would, on average, put horrible players on just your team? What about those 6 people you played against? Why should they get good players, but Blizzard single you out?
In fact, the other team has 6 random players you can't control, and your team has 5 random players. If you always play at a high level, your team has a guaranteed good person, and the other team does not. So shouldn't it favor you?