yes, players can do a lot of stuff npc can't but that's game play - if npc have stamina like players then I wouldn't care about the other stuff they can do.
You go swing a log the size of yourself a couple times and see how tired you are. Npc stam - they can't chase you or hit you endlessly - as mentioned the troll with big log swing swing, run run, swing, run.
at this point player has to find a spot to recoup stam or use a potion as the troll comes running at you again with another log swing of endless stam. - example