It really isn't much fun being drawn against the same team again and again and again (
B557189 6 on Living Lands 4.1 ,
B557199 4 on Comet Catcher Redux v3.1 and
B557217 4 on Cold Snap 2 ) when that team is consistently higher rated than the randoms pulled together to fight them. I'd like to think those games are less than stimulating for the team players as well, though can't rule out the possibility that they're doing it purely to stomp generally worse players (even I find seal clubbing cathartic, especially after a run of games that I never had much chance in).
If matchmaker is about "competitive" play, then the playing field should be as level as possible. Teams likely on the same voice communications have a major advantage over random individuals (however individually skilled) who aren't. I would favour barring teams from matchmaker (but by all means do whatever promotion, UI redesign or anything else to enable teams to easily play together in custom games).
Perhaps this could be revisited should the game acquire a large enough pool of players to consistently provide double digit queueus in matchmaker (meaning that chances are you won't be drawn against the same people over and over regardless of their team status) but right now, I think they do more harm than good.
That said, yesterday was the first time in a while I've been drawn against the same high rated team over and over. Though it has a big impact spoiling a particular gaming session, I don't actually know how many times teams face un-teamed players. Essentially facing teams is a low probability, high impact problem (a black swan issue). It spoiled my gaming session yesterday, but the days before I had some good runs.