And how does your point in the last two paragraphs proves AC usefulness again? Concealment is not AC (and its miss effect has always stacked with it) and neither is PRR (which derivates mostly from the type of armor you are wearing). A 50% chance of being missed has always been possible to achieve - specially because you COULD receive a displacement buff from a caster.
If you are saying the system is more balanced than before, I'll agree with you there, but it's not my point at all. My point is that the current system is an aberration that is not DnD and there is no reason why it should be this way when a few changes in the old system could be made to correct it.