Edit: Some mistakes. It's hard to review any customizable card because it's actually a multitude of cards all in one, with different interactions with all the folks of arkham, so lets fire my shot and see what I can work out.
So, in a vacuum, the base card is terrible, you probably should not ever include this thing in a deck. dont have 4 resources to spend on 2 health and 2 horror, that's a terrible deal at any level and never worth it beyond some very, VERY extraordinary campaign starts where you've dealt yourself some unusual pain with cards like In the Thick of It or Arcane Research and you NEED some soak to compensate.
This means then that we really are only looking at this card in the context of the upgrades. All of the upgrades are in the afforable 3 XP range or less which makes them available to off-class characters like William Yorick or Diana Stanley. So, lets have some fun!
First off, a baseline upgrade that by itself is invariably good: Hexdrinker.
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Hexdrinker gets you a card everytime you take treachery damage. This right here is often going to be worth the 3xp investment and 4 resource cost, it'll easily draw you 2 cards, often net 3. 4 Resources to save 3-4 life and draw 3 cards is just extravagantly nice.
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Hexdrinker + Protective runes = The 4 card draws become almost automatic, especially in a 4 player game.
Obviously the +2 health / Sanity upgrades combine very nicely with Hexdrinker+Protective runes to create almost absurd card draw but I'dd argue that, because of the exhust clause, you need to curb your thirst for cards just a bit and lean more into the tanking aspect.
Second up, the other card defining baseline upgrade: Armor of thorns.
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Armor of thorns suddently slots Hunter's Armor into the passive damage archetype that rose to some prominence with William Yorick and his trusty doggos. Picture this: a Hunting Nightgaunt spawns on you when you have Guard Dog and Hunter's Armor out, instead of attacking it twice, you attack it once and then just move or investigate, triggering an AoO, killing it with retaliation damage. There's nothing to dislike about that for sure.
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Armor of thorns + Protective runes is not the wondercombo that it is with Hexdrinker, because without the other "spike" damage triggers, dealing only 1 damage often isnt enough. Even so, every now and then you might be able to ask a friend to engage a Whippoorwill that can then be killed off easily.
Again, like hexdrinker, the +health/sanity upgrades also may not combo as nicely as you'dd like, because frankly, even if you're actively triggering enemy attacks, you're often just not going to be attacked 6-8 times in a game. So again this is less about retaliation damage but a bit more about actual tanking.
Third up, the last card defining upgrade: Protective runes.
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Protective runes turns Hunter's Armor into a communal health pool, which is awesome. All of a suddent you can act as a living shield that moves around and covers harmed friends from danger, love it, like it.
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Protective runes + Health/Sanity upgrades = Bigger health pools, love it.
When you add the other upgrades, Hexdrinker, Armor of thorns. Protective runes becomes a routine way to benefit off of the "mister tank" role or to burn down enemies slightly faster sometimes. Perhaps the most major downside to taking Protective runes is that off-class folks cannot afford the level cap to combine it with the other major upgrades.
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A major point to worry about is that Armor of Thorns and Hexdrinker interfere with each other, both of them "cost" the armor's lifepool, both of them exhaust the card, IF you intend to take both, the upgrade path is then probably:
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Hexdrinker/Thorns -> Health/Sanity/Protective -> Health/Sanity/Protective/Lightweight -> Hexdrinker/Thorns.
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That said, I'dd like to argue that once you've spent 5 or 7 xp on it, you can probably just stop and be happy with it like that.
As a note on the unmentioned upgrades, Enchanted and lightweight, the former is primarily a choice of slots, which might seem superfluous but then you realise that it might interact interestingly with Dragon Pole. Lightweight meantime is less a priority upgrade than it is a capstone after you've gone for either Spikes or Cards.
To name some names, here´s some character that can seriously look at Hunter's Armor for nice builds:
Lastly, anbody who can take the Protective runes variant should legtimitately consider taking up the tank role, Carolyn Fern and Vincent Lee are both the kind of character that's trying to protect the team and this is a pre-emptive way to do so without taking any risky skill checks.