I'm not particularly impressed with "Empire" technology. Obviously, what they have done is find a few items of tech that are essentially bulletproof, and they have modeled their society around them, much as the Roman Empire was built on the soldier's short sword.
The Lightsaber is a useful tool, similar in rugged dependability to an electro-magnet. It is the energy density that is the key to it. If you think a "phaser on overload" makes an explosion, you haven't seen anything until a lightsaber can be made to cook off.
It's darn hard to do, though. They aren't designed to operate that way.
Essentially, the lightsaber is a portable, extendable event horizon. Thus, in operation, it is not depleted of energy, but gains energy with even its passage through the air. By extending the optical path of the event horizon, one can make a blunt knife which cuts through anything. It is the equivalent of a high-speed, high-current, plasma torch with acid etching.
This explains why two lightsabers don't mingle. Each event horizon is tying to dominate its own area of influence. They become like similar pole magnets repelling each other.
Shielding against a lightsaber is difficult. It requires force field enhanced materials which are not disassembled by an event horizon. As I said, difficult.
But the tool itself is quite simple and useful, as has been shown. It is totally ineffective at long range, however, and would be inappropriate for starship defense.
If our boys in Iraq had to go up against Jedi Warriors, I would recommend the use of triple barreled single shot rifles. The pattern of three bullets arriving simultaneously, with a slight spread between them, would be a challenge for even the most adept Jedi to counter.
Haven't gotten around to figuring out how to do either yet. Not sure I want to be setting up "event horizons" anywhere near our Ship. At least any damage from a beam weapon targeting molecular interactions would be localized to the max trasmission distance of the beam and would eventually be absorbed by enough mass in its way.