So when trouble appears, as it must or there's no adventure, do I nerf the NPC stats or plot-device them out of the way so the PCs can do all the fighting? Tough call.
I've been adamant with this Star Wars campaign that I wanted the story to be right first, and that game mechanics would come after, and so far that's been relatively easy to maintain. But this time, it's a little tricky even from a story point of view. Luke and Kyle are veteran Jedi warriors, they should naturally be tougher than the heroes at this stage, otherwise why are the heroes bothering to be their students, right? At the same time, you can only have "rubble falls, separating you from the NPCs" or similar stuff happen so many times before it starts to become a real obvious plot device. This was actually a big problem whenever a major film character would show up in the Jedi Knight computer games: they'd appear, have a cut scene and maybe fight alongside you for an encounter or two, then disappear again until the end of the level "prepping the ship for takeoff" or "trying to find another entrance" or whatever.
Interestingly enough, DMG 2 for 4E has a whole chapter on mechanics of "nerfing" high-level characters so they can run around with lower-level characters for an adventure or two ... I might adapt those. What makes Luke and Kyle masters isn't just their high BAB and a bucket of hitpoints, but their variety of powers. It's a thought, anyhow.