I think main problem is offense, mainly because it's fixable and needs some philosophical changes from how we go about it.
From a defensive standpoint, I think most of our problems have come from how we handle our unit rotations, often putting together ineffective big man units, and starting Terry does us no favors particularly when playing alongside Rondo who likes to gamble frequently.
When Terry is paired up with Lee, he gets the PG defense assignment, which is usually a much better situation for him.
It's for this reason why I think Bradley will have a very good impact on our defense. Not only is he an elite defender, but it'll put our players in better situations to succeed from a rotation standpoint.