There's a problem with the current armor system: It's really overcomplicated and not all that deep.
While I'm not in a position to add depth to the system, I'm at least able to take out the excess complication.

Introducting the Armor Overhaul Patch. Armor is simplified to defence points. 1 Defence point means 1 damage reduced from a hit. However to keep things interesting, there's a few modifiers:

Iron and steel are strong and gives +10% damage reduction.
Meteoric Iron is only slightly better than normal iron in its stats.
Gold and Silver also give increased damage reduction as well.
Bismuth Bronze is worse and Black Bronze is better than Tin Bronze.
Antique Armor takes the stats of Steel Plate, but the broken versions fare worse off.
Platebodys/Gambesons/Leather give +50% damage reduc (since tier no longer affects damage)
Scale has been given a buff to better match its design. It now gets half the damage reduction of platebodies.

The defence points are really intuitive and are based on the armor type and the material used to make them.
You should have almost no problem figuring out just by looking. Here's a quick overview:

Steel Plate: 15 Defence and 60% reduction
Iron Plate: 14 Defence and 60% reduction
Bronze Plate: 13 Defence and 50% reduction

Steel Chain: 12 Defence and 10% reduction
Iron Chain: 11 Defence and 10% reduction
Bronze Chain: 10 Defence
Gambeson: 5 Defence and 50% reduction
Leather: 2 Defence and 50% reduction

Be careful, the old penalties are untouched, only defence values were changed. Even though you no longer take extra damage from higher-tier attacks, your armor will still take increased durability damage from an attack that is higher tier than the protection it provides. Trying to tank Nightmare Drifters with a T1 leather will rip it to shreds in no time. I don't even try to balance for PVP, so swords won't do any damage to players wearing higher tiers of armor. You'll need to deplete the durability first. Maybe this can be addressed later with a "Weapons Overhaul Patch" but honestly I just don't care about PVP interactions.