It feels to me more that two-handing is just really weak. dual wielding is fine if comparing a trade-off against a sword&board defensive style, you give up an appreciable amount of resistance to almost all damage for an extra chunk of like 50-60% damage if accuracy modifiers and losing crit and armor pen are penciled in with fudge values. it's just that two-handing loses in both defense and damage to its competitors and there's no reason to ever do it because you can do better at both in other ways. The weapons themselves are... questionably balanced, I think is the issue. Just looking at stats, and based on my own experimentation as both Thief and Warrior:
Dual Short Swords:
Primary is Accuracy 15, Crit 10, ArmorPen 10, 32 damage
Secondary: accuracy 0, crit 0, ArmorPen 3, 24 damage
I don't have the game's damage calculations on hand to figure out numbers accounting for accuracy, crits, armor pen, etc. of course, but this is about 56 damage if you assume the modifiers aren't taken into account.
Using Daggers:
Primary: Accuracy 10, Crit 15, ArmorPen 15, Evasion 5, 28 damage
Secondary: Accuracy -5, Crit 0, ArmorPen 4, Evasion 2, 21 damage
Bit less accurate and damaging, but a bit harder to hit and better against armor/when crit fishing. 49 damage versus 56, and Evasion 7 is easy enough to count without needing to know combat calcs.
Franisca:
Primary: Accuracy 0, Crit 0, ArmorPen 5, Evasion 5, 30 damage
Offhand: Accuracy -15, Crit 0, ArmorPen 2, Evasion 2, 23 damage.
Seemingly the inferior option. 2 more damage for a lot worse accuracy, crit, and armor pen.
Comparatively, a two-handed combatant:
Pike: Accuracy 10, ArmorPen 5, Crit 0, Evasion 10, Damage 35.
Poleaxe: Accuracy -10, ArmorPen 0, Crit 0, Evasion 5, Damage 40
Hunting Bow: Accuracy 10, ArmorPen 0, Crit 0, Evasion 10, Damage 28
Warbow: Accuracy 5, ArmorPen 10, Crit 0, Evasion 10, Damage 32
In general you have less damage output compared to dual wielding, worse accuracy, worse armor performance, and worse crit, in exchange for some evasion. But dual daggers gets you 7 Evasion when dual wielding which does away with that 'advantage', while still having at least a bit better performance everywhere else.
Sword&Board:
Shortsword+Hoplon Shield: Accuracy 15, ArmorPen 10, Crit 10, Evasion 10, PhysResist 10, Armor 5, MagicResist 5, Damage 32. (Tower shield for +5 Armor -5 Evasion, Wicker for -5 Physical, +10 Ward, +5 Magic Resist)
Curved Blade+Hoplon: Accuracy -5, ArmorPen 10, Crit 5, Evasion 10, PhysResist 10, Armor 5, MagicResist 5, damage 35
Battleaxe is literally just an inferior Shortsword.
Dagger + Hoplon: Accuracy 10, ArmorPen 15, Crit 15, Evasion 15, etc, damage 28
Sword&Shield has 3 less damage than, say, the Pike, for significantly better general defense. Poleaxe has a sizable chunk of extra damage, but much worse in all other properties. Warbow is worse or equivalent at every stat. etc. etc.
dual wielding gets you more damage per round with any combination of short swords and daggers than what a two-handed weapon will provide, and generally with better accuracy, anti-armor, and crit. You're just slightly less defensive. But one handed weapons paired with shields gives you just slightly less damage than many two handed weapons (especially if accuracy can be taken into account and you have a Shortsword), for better defense.
I think what it boils down to is that Shortswords are just far too good, or perhaps all the other weapons are much worse than they should be. Other weapons have SLIGHTLY more damage in exchange for inferiority in basically all other aspects, and Shortsword makes up the damage by being Light and just dual wielding, or can make up a defensive deficit by just having a shield without any real problems for end damage output. After Shortswords Daggers are probably the next best weapon for damage output, and are probably the best defensive weapon because they come with Evasion and can be stacked with a shield.
tl;dr: weapons need a serious rebalance in general. Shortsword is practically the best weapon no matter what, because defensively you can chuck on a shield, offensively you can dual wield them. Two-handed weapons probably need a buff across the board because right now they're kinda just an inferior bastard child of dual wielding and S&B combat, and worse at both. All weapons that AREN'T the shortsword probably need a buff, at least comparative to their price. The Curved Blade is terrible and is also the most expensive weapon available. Weapons seem to work on a principle that a few points of damage are more valuable than practically every other stat, which i disagree with based on combat testing. A Poleaxe, the strongest weapon, might do around 50 damage to a light weapon Shortsword's 40, and the Poleaxe is going to miss a lot more, do worse against armor, and crit much less frequently. It's hard to say if two-weapon fighting is 'too strong' offensively when I'd probably choose to just wield a single shortsword and shield over most of the two-handed weapons for offense.
In actual combat you have a real risk of losing fights against the Harpies, even if you're dual wielding. Just depends on your luck, unless you happen to have Cleave, in which case you still very well might lose if the Wingleader sings everyone back onto their feet. So Dual Wielding doesn't make combat a cake walk, nor does tanking with sword&Board, but going two-handed makes it a lot harder on you.
Also currently it's possible to glitch the game with inventory shenanigans that I did on accident, so you can throw a Light weapon into the second slot without it taking any off-hand penalties. So that's neat.
