Howdy Skip,
I have a question regarding burst enhancements, vorpal enhancements, etc. These enhancements activate when you score a critical hit. My question is this: Will the Improved Critical feat or the Keen weapon enhancement, which both increase the threat range of the weapon, also apply to the burst/vorpal enhancement?
Yes (but if you want to bar that in your game you won't get any grief from me).
There seem to be two sides to this argument.
1) The burst/vorpal enhancements use the end-result threat range of the weapon (i.e. they take into account Improved Critical or Keen).
This one's technically correct.
2) The burst/vorpal enhancements use the original unmodified threat range of the weapon.
This one probably is less problematical in the long run.
Skip Williams
RPG R&D