Subclasses, Part 1
<insert Mel Brooks joke here>
Path of the Beast
Because Totem Barbarians are just Larping. A psudo lycanthrope subclass. Or Wildshape as through the lens of a non-druid.
Form of the Beast
Interesting note: They are swap-able. Also none of these have a to-hit formula or listed bonus damage from anything. Just the damage die. They are called “Natural Melee Weapons”. Are you proficient in these attacks? Do they count as real weapons so you can get your rage damage bonus on them? Unarmed Strikes are called “melee weapon attacks” but don't count as weapons.
Bite
Self-Healing? For a Barbarian? That's kind of broken, especially at later levels when the barbarian can be permanently enraged and just go around biting everything all day long and never die. On the flip side, if it was temp hp instead, you would grow out of it by level 5. One of those weird abilities where mechanic isn't really salvageable in it's current state due to how the system is limited. Maybe make the bite it's own bonus action attack, then have the self-heal become a once per short rest thing that heals for a lot of scaling damage instead of a slow trickle.
Claws
Two attacks for the price of one. Only a tempting option if you get rider. Otherwise just use your greataxe. Or longsword if you can't use a greataxe.
Tail.
The Thagomizer deals 1d12 damage and has reach, which is nice presuming you get riders. More so for small races who can't get that kind of die normally. Even then it would rapidly go down in usefulness after level 5, when barbarians have two attacks, and get access to feats.
Bestial Soul
Obligatory natural magical weapon damage resistance bypass.
Jumping seems kind of meh compared to the other options, but at least you can swap it out on a short rest.
Infectious Fury
Reminds me of Old Yeller.

Important tidbits: Scales with con (secondary stat for every barbarian), causes creatures to lose their reaction and hit an ally, or just deals a bunch of psychic damage instead. Why psychic damage, shouldn't it be necrotic because it's an infection? I know it's just mind control, but not every form of mind control is based on mental energies.
Call the Hunt
Everybody gets Reckless attack! Your elven crit-fisher will love you for this.
Thoughts:
A bit of clarity is needed on these natural attacks. Also, just make them bonus action attacks. I know the Barbarian is bonus action starved, but these attacks have no way of being modified at higher levels. No feats, very few magic items, not even a Magic Fang spell to help them out. As a bonus action, they would at least save you the cost of a feat.
Way of Mercy
Not to be confused with the Way of Mercer. This subclass seems to be vaguely inspired by the old Way of Tranquility
Merciful Mask
Ah yes, because monks were missing out on that sweet Plague Doctor aesthetic, or would that be ascetic in this case? Who knows, maybe the entire subclass was just the set-up for that joke.
Implements of Mercy
Because you are a Doctor, you can poison people. Are these monks the Doctors that Anti-Vaxers were trying to warn everyone about?
Hands of Healing
More short rest healing? They just really want to break healing I guess. On the plus side it doesn't eat into the action economy too badly. You can still punch three times and heal in the same round for the same Ki cost.
Hands of Harm
A Ki Smite. As if monks didn't have enough ways to decimate their Ki pool. On the plus side, this one does better than breaking even, because you can burst it for 6x damage on a crit provided that the target is poisoned. Now if you only had a way to reliably poison targets.
Noxious Aura.
I've met people like this at conventions: You have the mystical power of B.O., which not only poisons and damages everyone next to you, it is also so thick that it helps deflect ranged attacks. Fortunately for everyone but you, it requires a Ki point to activate. On the plus side, having it active means you are conserving the rest of your Ki for Hands of harm.
Healing Technique
Lesser Restoration riding on your healing hands. Too bad it's at level 11, you could have really used this at like level 6.
Hand of Mercy
This ability is interesting. It's super powered Feign-Death that you can inflict on any creature, including yourself. It will inspire and require out of the box thinking for sure.
Thoughts:
This subclass has two problems, well three problems.
The generic Poison Problem. Half of this subclass gets shut down in the wrong campaigns. At least you still have stunning fist to fall back on. But it's still a dissatisfying experience when the fun things you signed up to do aren't a viable option most of the time.
A problem with Ki, until level 6 you are totally Ki starved. You want to Flurry of Blows cause that's “The Monk thing.” You want to Hands of Harm because that's your subclass thing. And you need to Hands of Healing because people are dying in combat all around you. At level 6 you basically have to give up on Flurry of blows, and most of the other core monk powers, but at least you get that passive poison cloud to help out on it.
The final problem, the Problem of Subclasses. This subclass wants to do two different things at once. Heal & Harm. Unfortunately, subclasses really can't do two things at once. This particular subclass ends up being 1/3 of a healer, which is not good enough to act like a healer (see the PDK for an example). Partly because of the mechanic they chose to tie healing into, and partly because they have to split subclass features between healing and poisoning.
Fortunately, there is an easy design direction that can mitigate most, if not all, of the problems. Instead of tying the Healing resource to Ki, make it a separate, daily resource. This allows the healing to have more oomph (because it's not short-rest resource), potentially hitting the half-caster healer benchmarks of
Revivify and
Greater Restoration (in some fashion). It allows the Monk to act like a Monk, because it's not Ki Starved. And finally it gives the Subclass a useful path to pick when poison isn't an option.
And seriously, let it heal more than just HP before level 11.
Oath of the Watchers
Quis custodiet ipsos custodes?
Tenets
This is the anti outsider/far-realm paladin.
Oath Spells
Most of these are spells that guard stuff or directly counter supernatural threats. Then you get weird stuff like
Chromatic Orb?
Is that supposed to be a stand-in spell? I mean, it does get around most resistances, but doesn't Divine Smite do that anyway?
Channel Divinity
Watcher’s Will. It helps break mind control effects, that's rad.
Abjure the Extraplanar. It's turn undead, but for anything from a different world. Kind of boring, but standard.
Aura of the Sentinel
Initiative aura? I suppose that works, but it seems, lackluster over any kind of aura that would help guard against supernatural stuff. Maybe if they threw in a bonus to perception checks.
Vigilant Rebuke
Your allies are really good at resisting spells, and this hurts people who try to hurt them. Unfortunately, not all supernatural powers are spells.
Mortal Bulwark.
It's brutal against an Outsider, but damn near useless against anything else. As a capstone, it ain't going to see much use, but still.
Thoughts.
This subclass is a bit too narrow in scope, it needs more generally applicable powers. Other than that, it's still a Paladin, so it's always going to be useful, and in the right campaign, it will dominate.
The Noble Genie
The Sha'ir, in non-wizard form.
Expanded Spell List
Thematic and useful, a bit of a rarity.
Collector’s Vessel
So you enslave some random creature and keep it in an itty-bitty living space.
Oh wait, no, you just create a mystical USB cord that connects your Genie-pod to a willing target so you can cast spells through them. Lots of tactical and RP potential.
Elemental Resistance
You and your new best friend have resistance to the element of your choice every long rest. Not quite as mechanically interesting as other warlock options, but undeniably handy
Protective Wish
You can swap places with your bound companion when either is struck. Handy if your companion is a Barbarian. Or I suppose it could be used in desperation to protect someone who is even squishier than a warlock, though I can't think of many who are.
Genie’s Entertainment
Finally something that actually collects.
It's basically
Banishment, but with no concentration. Also, if the poor target is unlucky, you can use it again. Really powerful.
Collector’s Call
A strange mechanic. It's basically divine intervention, but less powerful. Also by default it's a coin flip (or worse), but you can make it easier on yourself with some character building cheese. It's just a bit weird to see something that can potentially get harder for you to do when you increase your level.
Thoughts:
I have much objection to this subclass, other than the strange capstone. Though I do wonder how often it will be used instead of the ever-popular hexblade.