I think a big reason for Rondo's improvement is his increased amount of minutes on the floor. He's averaging 43 right now and averaged about 33 during the season.
If you take his 11, 8, and 5 numbers for 33 min a game, he would have gotten 14.3,10.4, and 6.5 if he had played 43 a game. These numbers are much closer to his playoff averages.
Combine this with no KG and get more rebounds and more scoring. Its not a fluke, its just Rondo doing his thing!!