But that is the natural progression for somebody who has been playing the game only for a few years. Defense is fundamentally easier than offense. Okafor, for example, was substantially underdeveloped at O as a frosh. Defense is substantially effort and awareness, and doesn't require any ballhandling skills.
That's Brimah's issue - he simply has not had enough touches in life to be good with the ball, whether it's rebounding or offensive moves. That will come with time.
My point is this - his lack of offensive prowess has everything to do with practice/experience and little to do with any innate limitation (which many guys do have!).
In 2 years he will be a legitimate offensive player, meaning we'll be dumping it in to him and he'll hit a decent percentage of hooks and such.