Two suggestions. When setting up the die, tighten the die into place only after the decapping pin has popped out a primer and is in the flash hole. This way the die is locked into place with the pin centered.
If you deburr flash holes, the result is a slight funnel effect on the inside that will help the pin find the hole.
I deburr by locking my electric drill in the vice and use either a tool or a 1/8" drill bit to touch each flash hole on the inside. It is rough as it touches and then smooth once the burrs are knocked off.
I once ran a test involving many differnt 308 loads that were split into 3 parts. 20 rounds (of each load) were ordinary relaods, 20 had debeurred flash holes, 20 had uniformed pockets. There were about 10 different loads tested. All but one showed a lower SD of pressure and velocity with the deburred flash holes.
Winchester cases. I would not expect to see any change with Labua or Norma cases, sicne they are about perfect.