Yes, it stacks, since you're not wearing armor. But unless you roll for abilities, you can still only get a 17 AC to start: +2 Mage Armor, +3 Dexterity (15, +1 from Monk), +2 Wisdom (14). It's better than just plain Dex+Wis, but not really broken when you realize that the Monk doesn't have Parry...