I hatched another 10 or so with no luck and have decided to give up. I did some more searching through forum posts and believe I may have found the answer, though no real way to confirm.
Apparently it is possible, with hacked/genned Pokemon, to merely change the ability to the HA without changing the underlying data that is passed down through breeding. So although the summary page for the Empoleon shows it having the HA, when breeding it is passing down its original, non-hidden, ability. I have no experience or interest in dealing with the programs that allow you to see or change these things so I can't confirm, but this seems the most likely answer as statistically it's nearly impossible to not get the HA after that many attempts.
Thanks to you both for your input.