A post to the Heroes of the Storm forums have more on Blizzard's ongoing efforts to refine matchmaking in their MOBA. Here's a bit on the latest:

Large parties in Quick Match are able to coordinate their hero picks, which can be frustrating for solo players who get matched against them. While this primarily occurs with full parties, we’re aware that this is a point of concern for some players. We’re currently investigating changes that will help limit certain types of team compositions from being formed when solo players are matched into a team. Something to keep in mind is that Quick Match is meant to offer players a wide variety of hero picks and team compositions. Just about anything can happen in this mode, and players who are looking for team compositions that follow the competitive metagame more regularly may want to queue for Hero League as an alternative.