Norms have no MM. Since I got G4 and went back to norms I notice a spread of Iron-Diamond is actually really common, and who is on what side may as well be random. Maintaining any control over norms really just requires you to be decently above average. I'd imagine Diamonds win most their norms with little effort when they try.
People say it's a seperate MM, but there's really no rhyme or reason to it, and if you play enough of it you'll really see that.
The harsh reality is that ranked is much better for casual play. Think of it as "Strictly balanced Q" rather than "Ranked Q", and let's be real, unless you're a pro, no one cares about your rank, it IS the casual mode. (Granted still tons of smurfs but it does a lot better job than norms)