Oh I see what you're saying. Well it comes down to how the DM rules on the following bullet point of Wild Shape:
- You choose whether your equipment falls to the ground in your space, merges into your new form, or is worn by it. Worn equipment functions as normal, but the DM decides whether it is practical for the new form to wear a piece of equipment, based on the creature's shape and size. Your equipment doesn't change size or shape to match the new form, and any equipment that the new form can't wear must either fall to the ground or merge with it. Equipment that merges with the form has no effect until you leave the form.
So here we have the problem that your Wild Shape form simply might not be able to wear a piece of equipment due to it's shape or size, and your equipment doesn't change shape. Thus it might either fall to the ground or merge into your form, at which point it no longer functions as normal.
So the difference is between the following two statements:
Unarmored Defense: You retain the benefit of any features from your class, race, or other source and can use them if the new form is physically capable of doing so.
Defense Fighting Style: the DM decides whether it is practical for the new form to wear a piece of equipment, based on the creature's shape and size.
The former really does come down to "does it make sense to me or not" as a ruling. The latter, however, runs into the fact that because your equipment doesn't change size or shape to match the new form, armor worn by a medium-size Druid is not going to fit on their body if they become, say, a mammoth.
And because Defense Fighting Style's wording specifies "wearing" armor and Wild Shape specifies that armor melded into your form isn't worn.
I still don't see how any of that
isn't the DM deciding what makes sense and what doesn't. Wild shape even explicitly says that in the text, it
doesn't specify what does and doesn't qualify. You just quoted it yourself: "Worn equipment functions as normal, but the
DM decides whether it is practical for the new form to wear a piece of equipment, based on the creature's shape and size."
That is a DM deciding what makes sense and what doesn't--what is "practical" or not. That the rules explicitly tell the DM to do so does not mean it is somehow not a DM ruling against something purely on the basis of what they think makes sense.
And, for the record, Mearls
said in response to the question "druid multiclass monk, unarmored defense apply to wildshape? ex wolf 13 nat AC +its dex mod and druid wis mod?" with the statement, "not in my opinion - natural armor counts as armor. use higher of base 10 + mods or form AC"
So I would literally be running it exactly RAW to allow the Druid to choose
either the form's AC or the Unarmored Defense benefit, which is what I was saying before.
Edit: In fact, this has actually been added to the official Sage Advice Compendium
document. Natural armor is one of the alternative AC calculations it lists:
SAC p 2 said:
Here are some ways to calculate your base AC:
- Unarmored: 10 + your Dexterity modifier.
- Armored: Use the AC entry for the armor you’re wearing (see PH, 145). For example, in leather armor, you calculate your AC as 11 + your Dexterity modifier, and in chainmail, your AC is simply 16.
- Unarmored Defense (Barbarian): 10 + your Dexterity modifier + your Constitution modifier.
- Unarmored Defense (Monk): 10 + your Dexterity modifier + your Wisdom modifier.
- Draconic Resilience (Sorcerer): 13 + your Dexterity modifier.
- Natural Armor: 10 + your Dexterity modifier + your natural armor bonus. This is a calculation method typically used only by monsters and NPCs, although it is also relevant to a druid or another character who assumes a form that has natural armor.
Being a Monk/Druid does not entitle you to merge multiple AC calculations. However, I would be
quite happy to work with a player so that they can build toward a Monk/Druid that can add 10+Dex mod+Wis mod+natural armor. Perhaps they can spend a feat if they wish to have things done short, simple, and sweet--though the feat would do far more than
just allowing these things to play nicely together in 5e, since feats are supposed to be chunky. (E.g., allowing half of Monk levels, rounded up, to count as Druid levels for spellcasting; allowing half of Druid levels, rounded up, to count as Monk levels for Ki points and martial arts dice; and allowing Ki points to be exchanged for Wild Shape charges and vice-versa.) Or, they could spend money on training and/or magic items to achieve similar effects, allowing them to spend their feats elsewhere (though such magic items might need to be custom-made or reclaimed from where they were lost).
Or they could do it through roleplay and checks, building up their new discipline over time through effort rather than through quick expenditure.
I'm cool with all of those things, because they all represent some kind of journey to a destination, using the rules themselves to express the story, and using the story to express the rules.
Edit 2, etheric boogaloo: That said, it would seem my "for the simplicity" thing is actually against the intent here, and you
are supposed to be using the creature's own Dex and the Monk/Druid's Wis. So, having discovered my error there, I guess that's what we do, even if it makes things rather tedious to calculate at the table unless the player is well-prepared. (In my experience, that's a binary thing--either you have one of the Crazy Prepared players who knows all this stuff back-to-front with notes and all,
or you have the far more common "uh, um, let me, uh, check the book? what page is wolf on? one sec...")