@DnDPaladinquestion : when something set base AC, like mage armor… does it affect the modifiers too or can we still add modifiers ? why ?
effect should specify if your AC becomes a set number, a set number + modifiers, or a modifier added to your AC

— Mike Mearls (@mikemearls) December 1, 2015

@DnDPaladin think of mage armor as creating a suit of light armor with a base AC of 13, + mods

— Mike Mearls (@mikemearls) December 1, 2015

@mikemearls also, why create monsters that can hit with like +15 if nobody can have more then 20 AC ? seriously, AC is weird in this edition

— Luc Charette (@DnDPaladin) December 1, 2015

@mikemearls ok… its not making any sense to me… then why say unarmored defense cant stack if the formula was already not stacking ?

— Luc Charette (@DnDPaladin) December 1, 2015

@DnDPaladin for instance, Mage Armor specifies 13 + your Dexterity modifier. That's your base. Modifiers would then go on top.

— Mike Mearls (@mikemearls) December 1, 2015