I'm not sure the East is really that much weaker. I mean it isn't like Butler, George, and Millsap were on good teams. Toronto should still be pretty good. Washington should still be pretty good. I expect Milwaukee to take a pretty decent jump into that group (i.e. high 40's, low 50's in wins). Philadelphia, Charlotte, and Detroit should all be better and will basically replace Atlanta, Chicago, and Indiana in the standings. Miami was on a 60 win pace for half the season and return their team (with the addition of KO).
Boston is still pretty clearly the second best team in the East (though may again end up as the 1 seed), but I think this notion that the East got a lot worse is a stretch. Some teams will move around, but I expect a pretty similar level of play from the East on the whole.