If you think Rondo's defense is the issue right now, then you really need to monitor these games better. Try a DVR if you have to and go back and replay things.
Keep trying to grind the ax with Rondo, though. Time & time again, its failed.
I think the biggest issues facing this team is that the offensive play has been choppy at times, especially in the half court. The team defense has been downright atrocious and inconsistent at times, and, lastly, this team just doesn't have the talent yet.