Well, if you have Ray or Pierce with the ball in their hands for an ISO, then their man just sags off rondo because hes not going to make a shot. That defender can come help on Paul or Ray which wont end up with a drive to the hoop either. It will be another forced jumper. At least with Rondo handling the ball, he can have his man all to himself, since the other perimeter defenders need to stick with Ray and Paul. There are lots of times where Rondo has basically been given a shot by the opposing player and with his speed got by him anyway.
It makes more sense doing it this way, since the defenders cannot cheat off, and if they do, then Rondo can find Ray or Paul as opposed to having Rondo's man free to help.
True, I was about to write the same thing... The problem is that our opponents found a way to "predict" Rondo's ISO, as it has been said... I'll talk mostly about Pierce, cuz I think Ray is more useful as a 3-point threat, distracting one defender's complete attention! Furthermore, he can take advantage of a pass off the screen more than any other guard...
However, I think that the decision depends on "the day"! I mean, Pierce is not isolating only at the end of the quarters, he does this thing many times during the game, a big(maybe the biggest)part of his offensive play consists of this style of offense, when he takes it 1-on-1 and hits the jumper or drives it to the lane! You can't doubt that, he creates offense on his own, he's been doing it all these years and, consequently, he knows how to do it better than Rondo or whoever else in this team... BUT(there's always a BUT)!! But when Pierce is struggling, he can't do this properly and he often ruins everything as well! It's a matter of psychology then, he turnovers the ball most of the times and this whole thing is a boomerang... When Pierce is playing well, there's no question, he should get the ball!! Even if he is not able to shoot(double-teamed), he'll go to the FT line or he'll find the open man and dish! And most of the times, when Pierce does that, the open man is KG and not Rondo! That's what I think I've noticed so far, I don't know if it's true...
On the other hand, when Pierce is struggling, I think Rondo is the best option, he's the playmaker after all...
So, my point is that the ISOs(if needed) should be done by Pierce AND Rondo, depending on how PP has been doing till that moment!! In general, we shouldn't be predictable so it would be fine if we use both players in this kind of situations instead of just Rondo or Pierce!!Like 50 Pierce- 50 Rondo...