The current weapon and damage system, while detailed, is actually rather unrealistic in some aspects.
To start off, it's not actually that easy to dismember bodyparts. It didn't happen as often as you'd think it would (despite what TV would have you believe). There are a number of factors that would prevent dismemberment from happening so easily:
- Little resistance; When limbs are struck, they don't offer full resistance (they get knocked around and give in)
- Bones; Bones don't break that easily. You'd have to be lucky and hit a joint (if you even managed to cut through the muscles)
- Layer of metal armour; You don't just hack through maille that easily with neither a sword or axe, let alone sever the bodypart beneath it
- Shields; Shield should offer way more protection to the entire body, especially to the shield arm. It'd be quite impossible to hit a shield arm at such an angle that the arm would sever.
- Weapons just aren't heavy enough; Weapons were usually designed to be fairly light (1H swords weighing at 1,75 - 2,5 kg) - meaning the blows would not have that much weight and momentum to it, thus solely relying in the wielder's strength to get through the tissue and bone.
That said, every weapon should deal some degree of blunt damage, which as already noted, should deal much more damage than it currently does. You don't just shrug off a solid hit to the chest with any kind of object - that would knock the air out of your lungs and have you gasping for breath for at least a few seconds. Not to mention the bruising or breaking of bones and muscles, and internal rupturing and bleeding of them - which have the potential of being pretty severe without necessarily damaging to arteries. I think you get the picture.