Yeah, we are watching clear evidence of a stressed out team. They've been broken by success, and no matter how much Doc yells at them, they physically and mentally can't put out the intensity that they used to. They will come to the playoffs and try to get up, only to find that there is no second gear.
Their half-court offense is totally broken. Go watch a tape from 1984 - the players grabbed the ball right out of the hands of the referee, even after a bad call, because they knew that the defense was going to pack into the lane (no D-3 seconds), and the only way to get a decent shot was to beat the other team up the floor before the defense could set itself. The only time the 2010 Celtics are effective are when they are running for this same reason. Unfortunately, only Rondo is fast enough to do it.
Sounds crazy, but if you try to run with Rondo, Ray and Tony/Quis at the core, and pick whatever two big guys you want to burn out in the process, it could work.