They seemed SOMEWHAT competent in the first two,
No, even in a new hope they were worthless. The scene that really drove it home to me was when Ben was killed. A group of Stormtroopers can't even come within 10' of hitting the main characters but Luke, an inexperienced farmboy who has never been in a battle before that day, using the exact same weapon, bullseyes the door control with a single shot.
You mean the moment where the Stormtroopers were "shooting at" the ship containing a homing beacon or the moment they were "shooting at" the group of crew about to board said ship that knew the location of the secret Rebel base and would never intentionally reveal it?
Yeah, strange - can't think of any reason they didn't manage to kill them all on the spot. ![]()