If you are wielding
two melee weapons, you can engage in
two-weapon fighting.
These melee weapons must be
light and
one-handed.
If you
Attack while you are two-weapon fighting, you can use your
bonus action to make
another attack, which must use your other weapon.
You
do not add your Ability modifier to this other attack.
You
can attack a different target, or perform another action (free action, action surge) before you use this bonus action.
So two-weapon fighting is initially a very square deal. You sacrifice:
- Extra damage from a non-light weapon
- Extra extra damage from a two-handed weapon
- Extra AC from a shield
- A bonus action
In exchange for:
- Extra damage from an extra attack
- Extra opportunity to hit with an extra attack
This isn't a bad trade! The most damaging light one-handed weapons in the game deal 1d6 damage, while a two-handed heavy weapon deals 1d12/2d6 damage – so you're giving up a bonus action to deal the same average damage as a greatsword-wielding knight, while probably using Dexterity instead of Strength and giving you two chances to hit. The shield guy's more difficult to compare, but let's set him aside for now.
Taking the Two-Weapon Fighting style as a Fighter or Ranger even lets you add your Ability modifier to the second attack, pushing it above the greatsword-wielder… although at that point they'll have Great Weapon Fighting and be dealing more damage themselves, and the shield guy has Defense or Dueling. Whatever. We'll leave this out and assume it equalizes, because the math on Great Weapon Fighting is too involved for my puny brain to put out on a forum post.
The problem comes in two forms.
- Extra Attack
- Bonus Actions
Extra Attack comes in at level 5 for Fighters, Paladins and Rangers, and it cuts the relative usefulness of Two-Weapon Fighting in half, because now the greatweapon guy is popping out 2d12+(Mod x 2) or 4d6+(Mod x 2) damage per turn with two attacks, and you can push out 3d6+(Mod x 2) damage per turn. You're both specced for damage over defense, and you're already doing worse than him! That's where it stops for Rangers and Paladins, and thank god for that.
For Fighters, it gets worse, because they get Extra Attack again, later on. And again, and again, and
again. At 11th level, the greatweapon guy is doing 6d6+(Mod x 3) damage per turn, and you're stuck at 4d6+(Mod x 3). Why even bother? It'll get even worse later on. Hell, the one-handing guy with the shield is looking better than you – if you both have your relevant Fighting Styles, he's doing 3d8+(Mod x 3)+6.
And he gets a shield.
It's actually even worse than that, because here we hit the second point – bonus actions. When you start off, this is a non-sacrifice, because there's nothing else you can really do with bonus actions… but as you proceed through your Class levels, you get quite a few things you can do.
As a Fighter, you get to use your bonus action to take an Action Surge once per short rest. Paladins and Rangers can use their bonus actions on certain Spells like Divine Favour and Hunter's Mark, as can Eldritch Knights and similar Archetypes/Multiclass options. Rogues don't get Extra Attacks, which keeps two-weapon fighting competitive, but
their bonus action is occupied by Cunning Action, which lets them dart around and hide.
You can't use your two-weapon fighting if you're doing any of these things. So you start off pretty balanced, and then grow badly. The stuff two-weapon fighting sacrifices becomes more valuable, the stuff it offers becomes less so. Diminishing returns in effect.
The relevant Fighting Style doesn't help at all with this. It just lets you add your Ability modifier to the second attack, so it's basically a trap once you move past 5th level. Even the relevant feat, Dual Wielder, is absolutely pathetic – you get +1AC, which is less than the shield you're giving up, along with the ability to use non-light weapons to change your d6 to a d8 if you don't mind looking a bit stupid. And that costs a
feat – other people get those too, y'know.
