I can't comment either on New Year's Eve, but we we stayed at the Cardona parador two years ago, Jan 5-6, after New Year's in Barcelona. I was surprised that it was about half-full, and we met several other Americans and Brits and enjoyed a lovely (and raucous) dinner with them.

It's a great parador, with a fantastic restaurant. Given its proximity to BCN,
I would think others would conclude that it's a nice option to the very inflated prices in BCN at that time. Go for it!