Well for one thing he is a much superior defender to all 3 of those PG's. People seem to forget that there is more to the game then just offense. He was probably the best defensive PG in the playoffs this year. He doesn't have to put up the numbers that those other 3pg's put up against you, because like you mentioned he is the 4th option on offense, but his defensive ability is what I think many Laker fans are overlooking.
Sure, he's a great defender but he will be defending Fisher or Farmar who doesn't score much anyways. It's not like he will be on Kobe or something.
I believe his dribble penetration will be the key, if he can dribble penetrate and pass out to allen or pierce, it will be deadly. But the lakers can counteract that by making him a jump shooter as he has shown he can not consistently make the 15-20 footer.
He's sometimes reluctant to shoot, but he shoots fairly well. According to nba.com hotspots, he's like 23-48 on his midrange jumpers.
The actual answer for the playoff is
FG: .414% 3FG: .294 FT% .756.
Both Pierce and Allen are better shooter than him. Of course the other teams want him to take the outside.
As a Lakers fan, I found those number pretty poor when he is the 4th and 5th options with your teams. Unlike Pierce and Allen, there is always someone with a hand up on their face, most of Rondo's shot are wide open shot.
If you look at Fisher's number in this playoff:
FG: .471% 3FG: .559 FT% .846
Similar to Rondo, Fisher is the 4th or 5th options, and he is shooting wide open shot all days, and making them.
If the Lakers were beaten by Rondo's wide open jumpshot, I think the fans will accepted that this is not their year.
On the hand, if the Lakers were beaten by Pierce's wide open jumpshot, everyone will want the head of Lakers coaching staff.