I think what we are seeing are just a natural flux of a player dependent on his jump shot. Millsap is a pretty good PF without his jump shot, but when he is nailing his jumper he becomes a top 10 PF. Sometimes it just isn't falling, but he continues to try it and he just ends up having bad nights. On the other side, there are stretches when it seems like he could make shots blindfolded and he has huge games.
I like that this year he isn't letting these fluxes get in the way of his rebounding and defensive effort like it seemed to do last year.