I think that's a general rule of story telling. One or two samurai, wandering the countryside, occasionally meeting others, works. Showing thousands of them in the service of some lord, not so much, unless they're quickly slaughtered and we get down to just a couple wandering around. Same with guns. An army? Boring. Armed former soldier who's a bit insane? Fun.
What about LOTR or Kingdom of Heaven?
I have no problem with Jedi in their hey-day but like Trey said, it's not the impression we got from the OT that they were just hanging around Galactic Central, giving speeches and chilling in the Senate. No exactly enigmatic monks there. But, I also like Jedi, and enjoy learning about them. I liken them to the Wizards in LOTR and have read as much as I can on the 5 Wizards in Tolkein's mythos. But, they are still mysterious and do not appear much. And we don't see two of them at all.
This, of course, supports Trey's argument in the commentaries that the Jedi should not be so prominent in the story. But, even if they play a small role, you could still have them show up in a final battle, of sorts, where they gather the Jedi from across the galaxy for a battle, similar to Aaragorn gathering his Dunedain kin for his battle at Pelennor fields. Again, its when you know that things are getting deadly serious when the Jedi, who we have only seen one or two of, martial together.
That's why I like the Old Republic setting of games/timeline/thing as it allows the Jedi to be very populous without affecting the OT-at all. But the PT is showing the fall of Vader and the Republic and becoming the Empire, so it shouldn't be about the Jedi at all, save for the small part they play in Anakin's life. And then Mike wrote a story...the end
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