Rondo in 2008 is not the Rondo being discussed.
The other very important thing to remember is that this isn't the team from 2008 either. While Rondo may have been perfect for that team, and been even more perfect for the team in 2010-2011, that is not really relevant. The question is who is the best fit for the Celtics in 2011-2012, and especially beyond.
I would argue, with the age of the Big 3, having another scorer like Paul will be more important to this team in 2011-2012 than it has been in the past, because we saw in the playoffs that these guys just can't carry the scoring load game in and game out like they used to.
And, then in 2012 and beyond, you will have a situation where suddenly Paul or Rondo would be the best player on the team, and will be getting a lot more attention as he likely will no longer be surrounded by superstars.
So, I would argue that Rondo's strengths of defense and passing won't be nearly as helpful in a situation like that. They are going to be asking whoever that guy is to be doing a lot more scoring, and defenses are going to make it a lot harder for them to get away with a 1 dimensional offensive skillset.