Quote Originally Posted by knight2k View Post
For crying out loud there is NO reason that ANY undead should be immune to this.
This spell only functions on undead creatures with 9 or fewer HD, just as it does in D&D. It's debatable whether that should be adjusted, but there obviously is a "reason" for it to be this way. It's an HD-capped spell, of which there are plenty in D&D.

Quote Originally Posted by knight2k View Post
Take less damage? Sure.
This spell doesn't do damage. It's save or die, with absolutely no effect on a successful save.