I did not know Taxanomy existed in this game until the Wiki; here should be perks that give you an edge against a specified type and, as a balance, give us some sort of weakness or debuff of some sort.
These are already accounted for, either with specific Powers (Banishment behaves differently against Ethereal and Construct enemies) or because the elemental weaknesses of particular enemy types are specifically targeted. There's a reason that the
Beast Killer bow does Blight damage: It's targeting that taxon's -75 Blight Resist stat.
Ashelander dialog options should have an additional benefit other than just smut; mediation removing 1 corruption is a step in the right direction if stingy (it should be an rng roll of 1-3)
Repeatable Corruption-reducing mechanisms are
designed to be fairly low because it's meant to be easier to gain the stuff than to lose it. It's spelled out right in the game's primary design doc. The big exception is the Cloister and that requires both Winterstem and a whole bunch of in-game time to balance things out.
Cleaning her should give you a buff to either attack power, crit damage & rate, or adds bleed damage to each attack, shafting could give you defensive buffs like getting 30% of fire damage taken as health
The game is designed to not have a gear treadmill, so making any weapon that's extremely overpowered (and giving one weapon the ability to grant multiple possible buffs most certainly would be) would either make that weapon game-breakingly powerful or it would require every future encounter to be balanced around it, penalizing players who don't use Ashe. Either way would be an incredible amount of work because one person didn't think a weapon that already is very good, unlocks multiple types of sex scenes and gets special lines on crits isn't Super Speshul enough already.
There should be some interplay between DoTs in a mechanical way. I do like that they effect at least two stats at a time but they could be more unique and less dependent on numbers; say if a unit is blighted and bled, they get an initiative penalty, bleed itself should stack; burn is really strong so it should have pros and cons even working against other dots by removing bleeding upon cast but increasing bleed damage taken by a percentage once the burn sticks, having a unit bleeding and burning at the same time should trigger the dots every turn another unit takes a turn. Frigid should stack and upon having 3 stacks should freeze the unit (Pokemon style freeze is perfect for emulation but with crush resistance getting a bigger buff)
This sounds like a fascinating idea... for a game where the focus is all on the combat and not on trying to find a nice middle ground between 'Smutty text adventure where you're just selecting options' and 'Fucking end this fight already, I've been stuck fighting these mobs for half an hour!'.
Also, damage over time already has a very significant use: Bypassing shield HP. If you inflict an enemy with Burning, Poisoned or the like, the damage those do is applied directly to health instead of having to work through any shield effect that the enemy has. It doesn't need a dozen edge case combination effects to be useful.