Overwatch’s Jeff Kaplan explains the functionality of matchmaking

Everything's fine.

Matchmaking is a big consideration for Overwatch‘s competitive play. Sure, it’s upsetting when a Quick Play match is filled with people choosing Bastion whilst you have no support or tanks, but it’s just a clear sign that this match will not be particularly good. When that happens in actual competitive play, it’s actively harmful to your progression. Director Jeff Kaplan took to the game’s forums to explain in detail how Overwatch handles matchmaking and the metrics it uses to evaluate player skill.

The short version is that Overwatch‘s primary skill metric is based upon your team’s success, not simply your own. Having a great killstreak without a single death might be impressive on its own, but if that didn’t contribute to your team actually completing its objectives, you weren’t doing much of worth. It also takes into account the differences in maps and in ping, since those can have a huge effect upon the fairness of the match. You shouldn’t expect to win every match, maybe, but if you’re losing consistently that doesn’t just mean that the matchmaker doesn’t work.

The patch notes for the PC update are live today as well.

Source: Official Site; thanks to Sythalin for the tip!