You also get to add your DEX Mod to AC to the shield. So 22 for the armor, and 22 for the shield. And yes, you should be able to fit all that onto a single character.
I never said it would be a good idea to get all this ****, but the title says "What is the cap on AC for a pure DoS come U11?", not "What's the most AC you can get while still be able to hold aggro?".