Republicans taking the Minnesota House wasn't that unexpected:
http://www.minnpost.com/community-voices/2014/10/why-dfl-will-lose-minnesota-houseIt was mostly a loss of rural seats where Democratic turnout clearly cratered. Even Dayton did kind of poorly in these areas all things considered, the map isn't all that impressive considering how safe he was considered, he even lost every non-Twin City metro county, the very bellwether-ish Olmsted county, and even some DFL-leaningish rural ones. Johnson didn't do that bad in hindsight, he basically matched Romney's numbers in fact.
But the good news is we already got marriage equality, medical marijuana and the more progressive tax structure, and the Senate means they can't go crazy with the amendment sh!t as a bypass around Dayton's veto like before.