Armor that reduces damage would only work if you took each armor and designed three sets of stats for each armor. One set of stats for each type of weapons blunt, slashing and piercing. Also you need a set of hardness vs each type of weapon.
Well if you took the example of chainmail armor. It does not make since that chainmail would reduce any damage for a blunt weapon.
But it makes sense that mail grants an AC bonus?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.