I really liked the illustrations in RedsArmy's attempt to rectify Rondo's shooting woes, it was a novel concept for an article to be sure. There are a couple of things wrong with the analysis that I thought the readers may want to know about (maybe not, who knows)...
First, pronating your wrist is not a bad thing for a shooter. The more you can flatten your wrist the more arc you will get on your shot. Dirk Nowitski is the primary example of this as his wrist is almost completely flat when he shoots. This isn't Rondo's problem as is should really help him to elevate the ball.
Rondo certainly leaves it in his palm too much, but even this doesn't have to be a big concern as long as he funnels the ball up onto his fingertips during the follow-through. Many good shooters don't get the palm separation until they are into the shooting motion with their hand.
The areas where Rondo does do things that are particularly destructive to his shot consistency are:
- Body position (shoulders and hips)
- Arm position
- Release angle
- Shooting motion
The first major flaw is with his body. Rondo turns away from the basket at a funny angle. Some good shooters do this, but it's best to have shoulders square to the basket and hips in alignment. This ensures consistently jumping straight up and down and not drifting on the shot. Turning your body away from the shot also promotes many of the release angle problems that Rondo has with his shot.
In terms of arm position, Rondo shoots away from his body with his elbow flailing out on almost every one of his shots. This causes huge fluctuations in left/right action on the ball. Again, there are good shooters who do this, but it is much more conducive to success to have the elbow tucked and square with shoulders and hips.
Rondo's release angle is his most egregious problem. Rondo shoots from the side of his head with his arm cocked like a catapult against his right ear. This creates a motion of "throwing' the ball instead of shooting it with a predominantly wrist-driven motion.
The way Rondo holds his release causes a ton of forward/backward inconsistency with his shot trajectory. There have been many players who have been good shooters without having Larry Bird's "arm fully extended" motion, but the key is limiting the extra motion and isolating the wrist as the principle generator of the release.
This brings us to the final element inherently flawed with Rondo's release. Rondo fully extends his entire arm from the shoulder all the way up through his release and follow-through on most of his shots. When you combine that with all the rest of the shooting flaws he has, you're talking about a shot that's drifting left/right, forward/back and getting sides spin on a good many of the attempts. This is why he has what has to be considered one of the most fundamentally poor shots from a point guard that I've ever seen. He's closer to Olden Polynice or Bo Outlaw than anyone should be comfortable with.
{styleboxjp width=200px,float=right,color=black,textcolor=white,echo=yes}To his credit, Rondo does work on his shot before every game{/styleboxjp} and the coaches have him eliminating much of the wasted arm motion, so though he still shoots next to his head, he is flicking the ball exclusively with his wrist in these sessions. Think about Shawn Marion, who shoots at chin level but still uses mostly wrist to release the ball. The less the entire arm moves the more consistent the shot will become.
{styleboxjp width=150px,float=left,color=grey,textcolor=black,echo=yes}It is typically best for a shooter to maintain as much of his natural motion as possible in order to keep the shot comfortable and familiar{/styleboxjp}. Based off of the fundamental errors in Rondo's delivery, I'd say it would be best to work on isolating the arm extension problems and continue to have Rondo work on using his excellent wrist pronation to get the arc on his shot. 
Eliminating that "catapult" motion would do more for his shot consistency than anything else while allowing him to continue to shoot from the position he feels most comfortable with, that being releasing from the side of his head with his arm cocked severely.
The process of ironing out Rondo's jump shot is not a simple matter though, as the above illustrates. All Celtics fans would love for Rondo to be the complete package and establish himself as the point guard of the future, but there is a reason that a player with his tremendous skill set fell so far in many scouts eyes.
Rondo has every other tangible and intangible facet to his game that one could ask for from the point guard position, but this element of his game sticks out like a sore thumb and is a principle part of a point guard's responsibility. 29 percent on jumpers isn't "poor" it's a major problem. This isn't easily rectified, but it's on Rondo's radar and he's got the work ethic to get through this problem and become the player everyone would like him to become. But this will be a process, not something that that Celtics fans should consider a matter of due course.