I responded to another post like this complaining about stones causing damage through armour.
We're not talking small stones, but if you look at the size of the projectile in hand, these are full on rocks. If you threw one of these at an unarmoured head, you could very well one-shot that person. Wearing plate armour, this projectile would likely trash your plate -- let alone only damaging you. Any bend in the plate could prevent the suit from moving properly, and a hit in the head would cause the helmet to bend in against your skull and on top of your concussion you would be dealing with a metal plate grinding against your head. If you're wearing mail, the impact of a blunt strike like this would be dampened somewhat, but it would still damage you. A chainmail head-covering of any sort would likely do little to prevent the resulting concussion.
So, in short, yes, you should take damage in certain situations, where appropriate. This is where maces and hammers have always shined, what they were generally used for in history.
I've studied history my whole life, as well, especially relating to weapons and armour. Definitely, blunt attacks have always been used against armour, and also piercing attacks were used with skill to hit vulnerable points. The latter isn't included in the game, and I'd hate to see the realistic play of blunt impacts on armour missing as well.