The important part it cannot be less than 16 that mean it can be more there is no description that forbid dexterity or shield.
I am playing dnd more than 25 years i know how much ts supposed to work.
Unfortunately, you are mistaken, and you don't. This is not an attack or a recrimination - many, many people have a decent understanding in general, and assume a lot of things from that, or get used to running things particular ways because that was how they or their friends first interpreted it. Running something incorrectly for 25 years does not make it any less incorrect, and if you have been assuming that all Ac calculation methods blend and stack, for the 15 year run of 5e, then please, take a moment; even if you continue to run it the way you choose to, or prefer to, it may still benefit you to know how the actual rules work, technically speaking.
Your Armor Class (AC) represents how well your character avoids being wounded in battle. Things that contribute to your AC include the armor you wear, the shield you carry, and your Dexterity modifier. Not all characters wear armor or carry shields, however.
Without armor or a shield, your character’s AC equals 10 + his or her Dexterity modifier. If your character wears armor, carries a shield, or both, calculate your AC using the rules in the Equipment section.
[...]
Some spells and class features give you a different way to calculate your AC. If you have multiple features that give you different ways to calculate your AC, you choose which one to use.
Bolding is mine, for emphasis. Spells and features can give you alternate ways to calculate your AC - these include Mage Armour, Barkskin, Unarmoured Defence (Barbarian), Unarmoured Defence (Monk) and Draconic Bloodline Sorcery, just as a few. The thing to understand here is that each of these is a method of deriving your final AC - and you can only choose one of them to use at a time, to the exclusion of all others.
So, the Draconic bloodline sorcerer monk barbarian (let's assume 16 in all relevant scores) with a Ring of Protection, a Cloak of Protection, mage armour, shield of Faith, and barkskin cast on themselves, and a shield available, has the following
options:
Mage Armour: "Base AC = 13 + Dex Mod" - If they use Mage Armour as their AC calculation method, their final AC will be (13 + 3 (Dex) + 2 (Shield of Faith) + 2 (Shield) + 2 (ring and cloak) = AC 22)
Draconic Bloodline: "Base AC = 13 + Dex Mod" - If they use their bloodline as their AC calculation method, their final AC will be (13 + 3 (Dex) + 2 (Shield of Faith) + 2 (Shield) + 2 (ring and cloak) = AC 22)
Unarmoured Defence (Monk): "Base AC = 10 + Dex + Wis" - If they use their Monk training as their Ac calculation method, their final AC will be (10 + 3 (Dex) + 3 (Wis) + 2 (Shield of Faith) + 2 (ring and cloak) = AC 20) (shields are not allowed, so we lose the extra +2)
Unarmoured Defence (Barbarian): "Base AC = 10 + Dex + Con" - If they use their Barbarian training as their Ac calculation method, their final AC will be (10 + 3 (Dex) + 3 (Wis) + 2 (Shield of Faith) + 2 (Shield) + 2 (ring and cloak) = AC 22)
Barkskin Alone: "Final AC cannot be less than 16; if final AC<16 then AC=16" - This
doesn't change our base AC calculation - its caveat is only concerned with affecting our AC
if it would otherwise be under a particular threshold... so just using Barkskin, their final AC would be reached using our standard, unaltered AC calculation method - (10 + 3 (Dex) + 2 (Shield of Faith) + 2 (Shield) + 2 (ring and cloak) = AC 19)
If you want to cross-check this, compare barkskin to other AC calculation methods - the others all tell you how to determine your Base Ac, and then offer caveats about things that negate them (such as using armour, or using a shield). Barkskin doesn't tell you that your Base AC is 16 - it just says that it cannot be lower than that number. Barkskin itself does not provide any actual bonus or increase to AC, with the exception of setting your final AC to 16 if it would be lower than that.
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BG3 does not handle its maths well, it tells players incorrect information regarding how it gets to the numbers it displays and uses, and is generally a terrible guide for understanding anything about D&D.
The entire
idea that Larian's
combat log, or tooltips tell players "10+1 natural armor +2 from mage armor +2 from dexterity" as an explanation is
utterly repugnant - because it's downright false! Your AC is 15 in this situation because it is "(mage armour) 13 + 2(dex)), and natural armour isn't a part of it because the mage armour calculation supersedes it!
