[AragornII]

OK, assuming that they do the same arrangement that they did in the books, Aragorn and Sam go after Frodo, Legolas and Gimli go after Merry and Pippin, and Boromir goes for Merry and Pippin too, who would Gandalf go with? I would assume that he and Sam would go for Frodo, leaving Aragorn free to hunt for Merry and Pippin. So, if Aragorn decides to go alone, he still has a better chance of saving Boromir. Let's just say that Boromir has a better chance of living if Gandalf is there.

alatar, I don't think that Aragorn could have filled Gandalf's role in Rohan/Orthanc. He doesn't have the fast horse that can bring Eomer in time. He was essential in being at the actual battle, and couldn't have filled Gandalf's place as Eomer(or Erkenbrand)-bringer.

Another point... if Gandalf hadn't been in the forest to tell Treebeard that Merry and Pippin were hobbits what would have happened to them? They might have been killed, and then Saruman is still out there because Merry and Pippin never roused the Ents to attack Isengard. What would the consequences been of letting Saruman live? Possibly a revival of Isengard and just Helm's Deep later in the story.