Note that some codices are available for some classes but not for others, even though they're not specifically listed as X-Class only.
Examples are that more than half the ones on Ord Mantell can't be obtained by the Jedi Classes.
That's only because you can't do missions on the starting planets you didn't start on. Those codex entries you are referring are from missions.
WolfpackAW, are you going to update your post with the stuff other people have mentioned? Like the Rodian gentleman on page 1. If you're only going to list things you personally have noticed missing, there's no point in contributing to this thread.