I was thinking about that skill, too.
And I think it says it increases the regeneration. This made me think there is probably a standard regeneration.
Going to a city in order to heal wouldn't be everytime you need healing. The idea is that you can carry a limited amount of healing items and use them accross a bunch of fights. You'd only go back to a city when the healing items are almost up. And frequently you'd also go back to a city for different reasons and you'd end up using the opportunity to re-stock the healing items.
Even if he doesn't regen for free on harder difficulties, it will be quite pointless if he can heal himself with just alcohol or if that darn skill allows free regen anyways.
The practical result is that multiple small fights would be no threat to you. Only fights that can deplete your whole health, along with your healing potential, would be a threat. This is bad, m'kay?
I have not noticed any natural regen in the videos I'm seen. That skill is probably just worded weirdly or its due to the translation. I also dont think that that skill makes anything "pointless", its has an opportunity cost since you are losing out on some other skill by taking that one.