Meh. At 15th level, that trick is already possible via Regeneration spell; and Lore Bards have been doing essentially the same thing to their allies since 6th level w/ Aura of Vitality. Variant humans may have been doing it since level 1 with the Healer feat.
With the exception that this one is completely at will, with no action requirement other than entering guardian form (something you would already do anyway as it is the whole reason for playing the archetype). It also garanties that your party would enter any fight with at least half HP. It is like giving Survivor feature from Champion Archetype for the whole party. And it also heals fallen allies. So, no matter how many hit points anyone within 30 feet of the ranger has, they will have a turn.
You're still vulnerable to insta-death, and getting grappled/kidnapped by a dragon to kill in isolation (away from help, including the aura); you're still vulnerable to petrification from a Medusa, or brain-eating by an Intellect Devourer, or getting Plane Shifted by a Rakshasa to the Elemental Plane of Fire, or getting shredded by a horde of zombies who auto-crit you to death and then start eating you on the same turn you go down to zero HP.
If your argument is that the dungeon master can still kill you if he wants, that is true to anything. Giving someone the ability to cast Wish at will still let the dungeon master kill you, but it does not stop it from being OP. (This was an intended exaggeration)
Bellow are my thoughts about the subclasses:
Horizon Walker
Nothing here caught my attention, other than highlighting the problems of TWF again.
Most of the spells are situational.
I think Planar Warrior should deal the extra d6 with no action requirement and the bonus action is only necessary for ignoring resistances.
Portal lore is completely campaign dependent, but that was probably the intention anyway.
Ethereal Step and Distant Strike are interesting, but the latter encourages kiting, one thing that I find very annoying.
Spectral Defense is Uncanny Dodge but better.
Primeval Guardian
My favorite from this UA, but it really needs some changes because it’s overpowered.
The spells are much better and less situational than the Horizon Walker ones, especially Entangle and Conjure Animals.
Guardian Soul is incredible thematically, but also incredibly overpowered. It really needs to specify that you can’t use Large Weapons. Although the Temp HP does not do much at low levels, but it kind of outclasses the only saving grace of the Champion archetype at high levels. I think this should go and they should add some kind of armor class to the Groot form. Something like:
“At guardian form your armor class becomes 17, unless it is higher, as your skin becomes as strong as wood. This counts as armor for the purpose of Defense Fighting Style. You can benefit from wearing a shield”
This gives the form a defensive benefit and stimulates strength builds, a thing I would really like because “Dexterous” and “Trees” aren’t two words commonly associated.
I also think they should add the ability to cast Thorn Whip while on Groot form. Maybe using your Strength Modifier for the DC.
I would also prefer to limit the usage of ranged weapons at this form. This should be the tanking archetype, and you’re not tanking if you are 100 feet away with a long bow. At least they should add an advantage for being melee.
Piercing Thorns is fine. Maybe the advantage to melee I just suggested could be here. Just make it only work with melee weapons.
They made a sneaky update to Ancient fortitude. I have the pdf open both on my PC and on my tablet. On the tablet it says it is only once per rest, on the PC it does not. That considered, I think it’s fine.
Rotted Defense is good.
Guardian Aura is giving Survivor Feature to the whole party 3 LEVELS EARLIER. This needs to go.
Scout
Spell-less Ranger take 3rd or 4th.
Nothing outstanding, but Rogue archetypes are all like that. Too much power on the base class. I think it is ok. It also stimulates kiting and as I said above, I don’t like it.
