Well, in Unearthed Arcana is introduced nice ruling that armor provides DR vs damage, or half of armor AC is DR. So examply Full Plate provides +4 'eguipment' bonus to AC and also provides 4/- DR. Also some DM's introdued ruling that critical hits whit piercing weapons allow negate armor DR.<br/><br/>Also Vitality and Wound points introduce some realism to injuries. Examply you can dodge all day long some blows but when you take physicall wounding hit, it is serious damage (and these rules is said that critical hit does weapon's damage directly to wound points).