Just on a coffee break and thinking about it.
Root armour seems to be overall the best armour, at least in my humble opinion.
Firstly, it's fairly easy to acquire early-to-mid game. Abominations are a pain, sure, but they can also be cheesed fairly easily with a decent shield and a handaxe, this means you can get it upgraded pretty quickly, and saves the requirement of Iron to be spent on weapons instead of armour.
Secondly, the benefits are great – sure it's armor rating is nothing to write home about, 1/3rd that of padded, but the resistance to pierce and poison means you're the king of ranged, and even deathsquitos will only tickle you. Bludgeoning enemies tend to be melee and you can probably outpace them, especially with the bow-encouragement.
Also a benefit to bows is huge, because it's the only weapon skill that increases both damage AND attack speed – in turn also speeding up your levelling with bows.
As for the weakness, the movement speed is the lowest negative in the game, and shouldn't impact because of your reliance on bows, and the fire doesn't apply within the swamp (because you're wet) and the fire-resistance wine overrides the vulnerability and is the easiest mead to make, requiring unprocessed Barley and cloudberries, both of which can be found easily and in large quantities in the Plains.
Lastly, because it's only a 3 piece armour set to get the bonus, you can wear a frost-resistant cape, meaning that with barley wine you're walking around with 4 descent resistances and a boost to arguably the best weapon in the game (the Bow).