One implementation I like a lot is in Age of Decadence. A tank plays very different from an agile dodger, and fighting a tanky opponent in heavy armor feels different from fighting someone who is fast and agile. You can even have a "tanky dodger" with the right gear and build, and those are a pain to fight (they're dodgy enough to dodge everything you can nail them with, and tough enough to shrug off your fast attacks).
I don't think armor is the complicated issue. It's other mechanics that are the root, but get conflated with armor. Dodging is the problem. It should not be a free action. AP/reaction should be required. Exceptionally fast attacks like bullets or lighting shouldn't be dodged without a special feat/talent. Critical hits are also another problem. In general, I think the concept should be thrown out or reserved for unique actions, like a Coup de Grace against a helpless opponent.
This is a good point, dodging is mostly pretty lame in that its pretty much free anti-damage.
I think someone here in the Codex once idealized a system where dodging would require space to manuever and "space control" is an important element. Dodging = Movement. If you have space to move, you can dodge. Want to someone from dodging? Herd them somewhere they can't move and manuever.
I think its interesting, especially because I JUST realized that it could fix one issue with dodge: Its either 100% useless vs AoE attacks (like a grenade) or you get inanity like someone "dodging" an explosion while remaining still.