Idea for armor: DR dice

Has this been done?  I recently had an idea that seems so obvious that I'm surprised I haven't heard of it being used before.

I freaking love Game of Thrones!  HODOR!

I've played around with DR (damage resistance) for armor in games before, and it always runs into some problems.  In case this concept is unfamiliar to you: DR is a way of representing armor and other forms of toughness by reducing damage to an enemy by a fixed amount. Although it ostensibly seems more realistic than something like D&D's AC (armor class) mechanics, there are places where DR breaks down.  

Empress (4th edition)

OK, so having editions for my own personal heartbreaker (much less using them here) is a little silly, but it helps me keep track of it for my own reference.  So when I glance at this post in the future, I can instantly determine exactly how out-of-date it is.

Follow the link in the caption below!

She's back!

I'm not going to assume that you're familiar with the first three editions, so why don't I summarize what makes Empress a little different from a D&D retroclone?

Abilities...

• There are four abilities instead of six; they are Strength, Agility, Mind and Spirit.  Strength encompasses physical toughness and Agility includes physical stamina (i.e. athleticism).  Spirit marries charisma with spiritual fortitude.  Mind folds perception into intelligence.
• Each PC has a Luck Die.  You can roll this to boost your own rolls, but that causes it to temporarily drop to a lower die face.
• Strength affects AC instead of HP, and Agility modifies HP instead of AC!
• Rolling high above AC let's an attacker apply combat feats, and they don't sacrifice the damage from the attack...sort of like Special Effects in Mythras.

Race and Class

• The only PC "race" is human, and there are only three classes: Warrior, Magician and Specialist.
• Instead of skills, characters choose specializations.  These are broad areas of expertise, and provide a big one-time bonus to all activities that are governed.
• Example specializations: Animal Handling, Stealth, Bushcraft, Athletics, Tinkering, Languages, Lore, Contacts.  Note that even the last three are not differentiated by sub-skills - they are all-encompassing.
• Most characters only have one or two specializations, but Specialists get a lot more.  Plus, they choose one specialization to keep improving as they gain levels.
• Warriors gets lots of HP as usual, but also, they are the only class to get better at hitting things as they level up.

Magic

• Any character can learn magic, but Magicians are much better at it.
• There are three types of spells: Mystical, Sorcery and Alchemy.
• Any spell may be of any type; the type determines the cost of magic.
• Mystical spells can be cast very quickly with concentration, but they are very fatiguing.
• Sorcery spells take a very long time to cast.  A small number of castings may be stored in foci, like wands or amulets, for instant release.
• Alchemical spells take a long time and a lot of resources to cast.  What they produce are agents - potions, powders and other gizmos - that can be used to produce a magical effect at a later time.

Exhaustive, or exhausting?  You be the judge!  Feel free to make comments or ask questions here.