Agreed. I find the phrasing really easy to understand.
Let's take a few Druids that have cast barkskin:
Druid A is wearing padded leather, have Dex 12, and a shield. Her regular AC is 11+1+2=14.
Druid B is unarmored, have Dex 20. His regular AC is 10+5=15.
Druid C is wearing hide armor, have Dex 16, and a shield. Her regular AC is 12+(max 2)+2=16.
Druid D is enjoying the Mage Armor spell, have Dex 16, and wears a Ring of Protection. His regular AC is 13+3+1=17.
Now, let's see how each of these characters are affected by Barkskin. Remember, the spell's only effect is to say your AC can't be less than 16.
Druid A can't have an AC less than 16, so her AC becomes 16.
Druid B can't have an AC less than 16, so his AC becomes 16. (See how easy this is?)
Druid C already has AC 16, so Barkskin has no particular effect on her: AC 16
Druid D has an AC higher than 16, and Barkskin certainly doesn't lower or restrict your AC, so: AC 17.
Mouseferatu got it right. Only way to be confused is to read things into the spell that isn't there.
If you all want to really interpret it that way, more power to you... but I find this to be completely against K.I.S.S. in my opinion, which is how I interpret pretty much all the rules in the game.
When I read the spell as-is... without trying to compare and contrast it to the words used to describe Mage Armor, and Unarmored Defense and then trying to make verbal equivalencies based on which words did and didn't appear in all these entries... at its base, Barkskin is giving you an AC of 16, the equivalent of chainmail armor. Just like it says... your skin becomes hard like bark for an AC minimum of 16. Your skin becomes the armor... you now have Natural Armor Class of 16 (to use the 3E parlance). So if the druid is standing there naked and gets Barkskin cast on it... its skin becomes like AC 16 armor. The spell's not looking at whether you have a DEX mod or not... it's not looking at whether you currently have a shield on or not... it's not looking at any other AC-modifying things that may or may not be present. Naked druid + Barkskin = AC 16.
And then it adds that it can't be less than that regardless of the armor it may be wearing. So even if the druid was to put on leather armor which gives an AC of 11... the natural Barkskin armor would supercede it. But then it's also important to note that the spell doesn't say that the druid's AC has a
maximum of 16 either... which to me simply means that the druid's AC wouldn't
drop down to 16 even if the druid was wearing other better armor that gave it an AC of 17 or higher. So for instance if there's something like +3 dragonscale armor in the DMG (just making up an armor for the sake of argument) that would grant a person wearing it an AC of 20... the druid's AC wouldn't drop back down to 16 just because they had Barkskin on. Like in 3E... you'd compare the AC granted by natural armor to the AC granted by regular armor, and the person would use whichever was higher.
And then once Armor was taken care of to generate the druid's AC... all the other things that could modify that AC come into play-- DEX mod, wearing a shield, cover etc.
Isn't the fact that people are questioning why cover and shields wouldn't seem work with a Barkskinned druid... thereby going against all common sense... a pretty good indication that making these weird verbal equivalencies to the wording of Mage Armor and Unarmored Defense probably is unnecessary, and also not intended? Because why
wouldn't a druid in cover get a bonus to AC? Or wouldn't gain the benefit of a shield? To me it makes no sense to suggest they would suddenly stop working just because the druid now has a natural armor class.
Now I would willing to grant one thing in this conversation... the argument that a Barkskinned druid would not get to add his DEX modifier to his AC. That might be the only one that maybe I could be convinced shouldn't apply. 1) because the spell doesn't say you can add your DEX mod to AC unlike MA and UD (but admittedly I have to go against my own instinct to not have to do detective work comparing and contrasting other different spells/effects, but so be it)... plus more importantly 2) because your skin becomes the numeric equivalent to chainmail, and since chainmail is a Heavy armor (and thus doesn't add DEX mod), I could see considering Barkskin functionally the same as chainmail and thus shouldn't gain a DEX mod bonus either. Combining these two points together, then yeah... I'd be willing to buy that argument that the druid might not get to use its DEX bonus to raise the AC.
But you'll never convince me that a Barkskinned druid no longer gains the benefits of a shield or cover just because they have the spell on them. That's going way past my sniff test and I find it makes absolutely no logical sense. But your mileage may vary.