I think Dwayne Casey of Toronto is getting forgotten about in Toronto. He's done a great job with that team this year, and has risen above the mediocrity in the East. This despite a major trade mid-season, in which his team was theoretically just dumping salary. He should be above Stevens, Clifford of Charlotte, and I suppose Scott Brooks, if we are to otherwise accept that Clifford should be above Brooks.
I'd also put McHale above CBS. Yes, his team got the talent this summer, but he's really helped get that team rolling in the last few months, including getting Asik involved again. I'd also give Budenholzer of Atlanta a bit more credit, unless you think he should be tanking his team for a better draft pick. I'm not sure how much more talented that Hawks team is than ours with Horford out -- mostly a bunch of role players.
But all in all, I think Stevens is properly rated as being in the top half of the league.