Rondo needs to shoot better and have a quicker release on his outside shot. If he improves in these areas, defenses will than have to adjust. That is when Rondo will really change the way he can impact the game.
But your criteria then, is pretty much totally subjective, unless you are going to give us your strict definition of when defenses are 'sagging' and when Rondo is simply 'open'. How often is this really happening?
Going over/under picks is not a useful metric there -- doesn't the pick setter get credit? What if that's a reflection of just plain stupid defense?
I find it mind-boggling to think that a player should be knocked for being smart enough to prefer to take shots when open rather than when contested.
I think VG is just pre-empting the counter-argument we sometimes see from Rondo-defenders: Rondo shoots a high percentage! But field goal percentages are not created equal. Rondo has been able to score at a relatively high percentage because through most of his career he's had the luxury of being very choosy about his shots. When it comes to jumpshots, he rarely shoots except when he's wide, wide open.
I take VG's meaning to be that for Rondo to really prove himself as a "franchise, build-around" type player, he has to show that he can be a focal point of the offense, not simply by dominating the ball and dishing out assists, but by looking for his own shot. I agree with that idea.
To me, Tony Parker is a much, much more valuable offensive player than Rondo regardless of the fact that he rarely gets double digit assists. He creates more space and more opportunities for his teammates because he's such a threat to score with the ball in his hands -- even though he's not an amazing shooter outside of 15 feet. His pull up mid-range jumper is just that deadly.
Steve Nash, similarly, was never a prolific scorer, but he was such a great shooter that he was always dangerous. That played a large part in the fact that he led some of the most potent offenses in the history of the league, in my opinion.