No-on ever thinks it through though - Armour as DR, as presented in Unearthed Arcana, is a terrible idea, and the sure sign of someone smoking excessive amounts of cocaine. Seriously, who wrote that shit?
So, we have three chaps who wrote shit nobody cares about, and, wait for it, Andy "I smoke crack!" Collins!
That rule results in people getting hit in combat all the fucking time, and the damage getting reduced by such tiny amounts that it will never matter. Ever.
The method below looks a lot better - they have a scaling AC bonus that isn't connected to their armour, except this in turn means that attack bonuses of those who ignore armour are wonky. At this point, everyone needs to have the Fighter BAB and even then, some things will need a Str/Dex bonus in order to hit, because suddenly their attacks are made against people with Touch ACs much higher than they're meant to be*. Meanwhile, no-one cares about the DR they get.
For the DR to matter, it has to scale with level. Why? Because the damage you receive, and the HP pool it's taken from, both scale. And at the same time, you need to remember to scale everyone's attack rolls to this new "Touch attacks don't exist" thing. Oh, and Rogues are basically impossible to hit under your system, seeing as they add their level to their AC and wore minimal armour in the first place.
*This is also a problem with the whole "We have different BABs, and different ACs to attack" idea. That was dumb, and at least 4E did away with that shit. I'll give credit where it's due.