Well if it's an HKA nnd of lets say 2.5d6. Then we add some martial arts DC's It can easily be 3-3.5d6. Thus averaging around 12 body per attack Killing anything hit hits on an average roll, except for PC's, important NPC's and things W/high body. I know things aren't officially dead till they're negative thier body, but I don't pay that much attention to mooks in my games at zero body they're out.
And the low damage count is backed up in the movies by Vader taking a shot of the arm, Ob1 not getting chopped in three by Dooku and it taking four hits to put down the Acklay in the areana on Geonosis.
Remember, as you once said, no one appears to have Resistant ed in Star Wars, so in melee combat all a big energy killing attack is ends up being, is a big NND.
As far as the not cutting through supes or thor....Yeah I really don't see that as a point besides a wierd meta system debate. I, and DOJ apparently as they wrote up the Lightsaber similarly, don't really care about that to much. And you know what, to hell W/it who says that a Lightsaber can't cut through Superman, as far as I know there is know president set for that...and hopefully there never will be .