Source: http://world-of-kwg.livejournal.com/209487.html

Basically, Storm made a post, where he asks people to present MM fail screenshots. Currently, there are apparently some issues with the matchmaker in 0.8.6, namely the fact, that since tier 10 heavies have the same MM weight as tier 10 arties, currently it is possible for one team to have two tier 10 heavies and the other two tier 10 arties. Storm is currently considering what to do with it.

I will follow this post to see, whether they come to some conclusion.