Conan does something like that -- any hit over a certain static amount will damage your armor, lowering its effective DR. Also, they added armor-bypassing factors for weapons, which makes combat a lot slower in some cases, but no more so than having lots of magic would have done.
The rule I ended up liking (although I'm in M&M right now, so all armor IS protection, I guess) was this:
- Go to VP/WP
- Armor provides DR, but only against WP damage
- Crit multipliers are dropped by 1 (x2 becomes x1, x3 becomes x2, etc.)
- Crits go directly to WP
- Crits that beat the confirmation Defense by 10 or more bypass Armor DR
Ergo, your swashbuckler is wearing a Chain Shirt (DR3), and a bunch of bad guys fire arrows at him. He's Defense 17 and has 63 VP.
- One bad guy hits for 8 damage. The damage comes out of VP, and there's no DR
- One bad guy rolls a critical (natural 20) and confirms with an 18. He does 3 WP damage, and the DR3 of the chain shirt soaks it.
- One bad guy rolls two natural 20s, critting and confirming with a 28. He does 5 points of WP damage, and the damage is not even slowed down by that armor.
If these were crossbow bolts (19-20/x2 normally), they'd be doing the normal damage, even on a crit. If they were arrows (20/x3 normally), they be doing double damage on a crit -- meaning that getting your bad ol' self critted by archers is not a good plan. Especially if they beat your defense by 10 or more on the confirmation roll.