I agree that "A diversion" was a fairly obvious line, but last time I went to see RotK, I noticed something. There are a lot of instances where characters state the obvious. A couple of examples I noticed (and I'm sure there are many):
- Frodo, when touching a spiderweb in Shelob's lair: "It's sticky!"
- Sam, looking at a doorway (if memory serves, the entrance to Mount Doom): "A doorway!"
- Pippin, when the Eagles swoop in to fight off the nazgul: "The Eagles!"
So, to be fair, it's not just poor Legolas who's doing it. Everybody wants to get a piece of the 'Captain Obvious' action.
As far as the fangirl thing is concerned, I agree that Orlando Bloom is good-looking and Legolas is good-looking, but, perhaps because I loved The Lord of the Rings even before the movie came out, I tend not to obsess over him. As characters go, Legolas is not especially outstanding; I'm far more intrigued by characters who appealed to me when I read the book.