With three Hall of Fame notorious offensively clutch players, especially Ray and Paul who are known for their heroics, shouldn't the offense be run through one or all three of them? Despite one's argument that "Rondo needs to become accustomed to pressure situations," we aren't the 2007 Celtics who need to be wasting time coaxing young players. We need to be focusing on winning basketball games, not grooming Rajon for post Big 3 years.
I agree with parts of your post. I don't really like the way that Rondo hovers around the perimeter late in the shot clock and settles for jumpers instead of drivig in and shooting or kicking the ball out. But while we aren't the 2007 Celtics trying to develop young players (and Rondo doesn't fit into that mold anyways) we're also no longer the 2008 team with a big three that's so good that they can beat most teams on their own. If this team wants to win the title they'll need Rondo to make big plays in the playoffs this year. They may as well start getting him ready now.
Despite Rondo playing an ever-growing role on this team, wouldn't you have felt just a bit more comfortable with Ray Allen or Paul Pierce taking that last look against the Clippers, and ultimately the decisive free throws? That's pretty inarguable. The Big Three is old, not dead.
Possibly, especially if the ultimate goal for our season was to win that single game against the Clippers. But if they have playoff aspirations it makes the team all the better if Rondo's been successful in some of those late game situations. If Rondo ends up with the ball in his hands late in a playoff game would you rather think "at least he's been here before", or "I haven't seen him in this situation before, but at least we beat the Clippers in December!"?