The only thing I missed is where armor will be. It's not a tertiary stat. I guess it's not the primary tank stat, would be somewhat weird. That leaves it as a... secondary stat on cloak/rings/etc only. Maybe enchant/gems, and the natural AC of shields and plate.
Personally, I'm not fond of gearing pure passive stats. Wasn't it the problem in dodge/parry? (aside worst case considerations with it, something armor does not suffer from)