So it says in Hard difficulty that you regen 50% health after combat, well I just had combat and took 4 damage, after combat that did not change.
So when it says regenerate, what does that mean, do I have to do anything, does it take time, it is working as it should? I am definitely on Hard not Very?
If your not getting healed after combat your on the correct setting and not the cop out setting 
But i would check if i was you , your supposed to get healed 50% on hard.
Nope on Hard, weird thing is I play games for fun, not something that people seem to do these days (not having a go at you, I know you are saying in jest), now people are obsessed with getting virtual badges to show to other total strangers in some odd, if rather desperate, attempt to be noticed. LIKE ME, SEE ME, FRIEND ME, LOOK AT MY GAME LEVELS!
I always feel slightly sad for the masses of people on the likes of multi player matches, shouting profanity, filled with unchecked bitterness and brittle pride, ‘fun’ seems to have become an insult, something for those who refuse to join the pack.
Anyway getting old but having fun too 
I think the heal is healing your character to 50% health (round down).
If your character has a higher proportion of health, there’s no heal at all.
On Hard difficulty you will heal up to 50% of your total health after a fight. So if you end a fight with 75% health, your characters won’t get any additional health back. I double checked this with the Bearded Ladies and they confirmed it for me.
No, that’s still wrong, implying you regain up to 50% of your total health. What it should say is: “Your stalkers heal back to 50% of their total health after combat”.