Someone drank the koolaid. This is what the devs said. It may even be what the devs intended. It is not what the devs gave us. AC is completely irrelevant now. EN/EH are a total joke, however much AC helps there is irrelevant, you'd beat them easily naked. In EE AC does nothing.
And no matter how good your AC is you cap out at 75% miss. You can no longer get away with maxing your AC in low level content and getting a 95% miss. You now take 5x the damage you used to. Ouch.