Whats the HP rule in this world?

I watched s1e1 and the first fight in s3e1. In ep1, the Rosamund Pike char tanked the thrown dagger to her chest, while humans die normally. The satyrs drops HP (and disappears?) when tanking her rock throw combo. In s3e1, the bleeding antagonist mage tanked 2 stabs but I assume not dismemberment since her students rushed to shield her from the blades coming in at her neck. Now that I think about it, rock throws seem to stop everyone in their track. Stopped Mother Mage from channeling, knocked out gate guarding mage, and deleting a hoard of satyrs. I suppose Im asking if the combat logic / writing is tight in this series.