What it basically means is that you'd need to roll two attack rolls for every attack you make, one to see if you land a hit, and another to see if the hit does damage.
So, for example, instead of AC 20, you would have DAC 5 and AAC 15. Any attack that roll higher than AAC but lower than AAC+DAC would count as hitting the armor.
I've already accounted for that issue. You only need a single attack roll, it's just that there's more granularity in the list of possible results. Granted, there are bound to be some edge cases where the system would start to behave weirdly, but it's better that what we have now.
I don't really see how that's better, unless you want to start modeling armor damage. Both systems would output the same result, unless you're going to complicate things further with different damage types getting partial armor penetration, shock damage, &c., which again is
needlessly tedious for a roleplaying game. As he said, what you're asking for is the sort of thing that would fit right in to a wargame. RPGs aren't about perfectly simulating every aspect of combat, they're about creating a good enough combat system such that it has versimilitude, so that it can be worked into the story they're building.
Again, you're trying to create a mechanic to make up for lazy roleplaying. If an attack was just below the target's AC, rather than saying "You miss," when they're attacking a slow, armored target, give a brief description of them denting the armor, or their blade skittering off scarcely an inch from a vulnerable joint. If you get to the point where people stop caring about the descriptions and just want to get on with it, the mechanic becomes redundant as well but can't simply be dropped for convenience.