If you had a dexterity of 30 and a wisdom or constitution of 30, with Unarmored Defense for Barbarian your AC while not wearing armor would be 10+your dexterity modifier + your constitution modifier for a Barbarian. Your AC would be 30 because 10+10+10=30. If you had a dexterity of 30 and were a Sorcerer of the Draconic Bloodline, you would gain the feature of Draconic Resilience, your AC when you are not wearing armor would be 13+ dexterity modifier. That means your AC would be 23 because 13+10=23. So if you were a Barbarian/Sorcerer multiclass, could your AC hypothetically stack to 33 because 13+10+10=33?