Questions about Duel Wielding

[Mgrancey]

I would agree with others, most classes either have something better to do with a bonus action than a weapon attack with an off hand weapon OR something better to do with their off hand: such as a shield; 2 handed weapon; or free hand for spell casting, components or motions.

I would expand that Monks and Rangers, on top of Fighters and Rogues, are the two other classes that would benefit from an off hand weapon. If I had a spell caster with a focus in one hand and weapon in the other I would be asking what is needed to cast a spell and say no, your hands are fully occupied when they need a material or somatic component.

[GavinRuneblade]

Though it was hinted at, I'll spell (sorry) it out: spellcasters don't have an empty hand for casting spells with somatic & material components. A cleric/paladin can use a shield with an emblem, but not a weapon. Sword bards can use a weapon as an implement which covers spells with material components that do not get consumed and don't cost money. That's it. This is usually named by character optimizers as the second biggest drawback with the bonus action cost being the top drawback. Even Mike Mearls the designer has tweeted that the bonus action cost is too high, as noted it completely ruins rogues by locking them out of their cunning action.

Also, the off-hand weapon does not get any stat bonuses without a feat investment and the feat is widely regarded as trash tier because it doesn't give anything new it just removes penalties. And there is no way to get a -5 to hit/+10 damage with the style. This makes it the second worst performing combat-style option for damage, only coming out ahead of sword-and-board protection. The developers have mentioned in interviews and had some tweets about wanting to revamp it so that it lands in-between single weapon and two-handed weapons, but right now it is behind both (excepting only for the defender choice as mentioned above). This even ruins the style for crit fishing because if you crit with the offhand weapon you end up with 2d6 damage (highest possible for a light weapon) instead of say 3d12+5 (with another +10 if you chose to take the -5 to hit) with a big axe. Usually you'd think that taking one extra attack per round would be useful for a build based around crits, but not when it is that trivial a result.

Light weapons are not at all "quite powerful" they are the weakest in the game doing only 1d4 or 1d6 damage, vs the 1d8 for a non-light weapon in 1 hand and d10, d12, and 2d6 for two-handers. There are no light weapons with reach, the closest is the whip which is d4 and finesse, but not light. And once again, as stated above, there is no way to give them -5 to hit/+10 damage which is pretty much mandatory for an optimized damage build.

Some players try to drop the offhand weapon for free to cast spells then use their interaction to pick it back up. Sheathing is an interaction so you can't sheath and re-draw in the same round. This is not technically either RAW or forbidden, so your ability to do so depends entirely on the DM's choice; Sage Advice author Jeremy Crawford has said that he would consider allowing it in his games, but didn't straight up endorse it. Many DMs have reporting using enemies to snatch or kick away the dropped weapons with reactions and readied actions.

Overall, two-weapon fighting is an option that gets chosen for flavor. Which is a perfectly fine reason to choose it.

[spoofer]

I would expand that Monks... are the two other classes that would benefit from an off hand weapon.

Monks can use their bonus action for an unarmed strike. Some of the ki powers also consume the bonus action, so monks do not do two weapon fighting.

[Mgrancey]

Ah right, sorry haven't played or played with monks much. I was mostly thinking they are about the only way to get sufficient damage from an off hand weapon once you get to a higher level.

I would agree that adding a bit to someone who goes for 2 weapon or sword and shield could use a bit more. Some thoughts I have had would be to give a bonus to DC on Maneuver dice for fighters on that follow that path, allowing the Bonus action for multiple attacks when someone gets a 2nd attack, bonuses to feint since 2 weapons would make it easier.

I think I had some other ideas but this was just a quick response in morning before work.

[GavinRuneblade]

Ah right, sorry haven't played or played with monks much. I was mostly thinking they are about the only way to get sufficient damage from an off hand weapon once you get to a higher level.

I would agree that adding a bit to someone who goes for 2 weapon or sword and shield could use a bit more. Some thoughts I have had would be to give a bonus to DC on Maneuver dice for fighters on that follow that path, allowing the Bonus action for multiple attacks when someone gets a 2nd attack, bonuses to feint since 2 weapons would make it easier.

I think I had some other ideas but this was just a quick response in morning before work.

I think Mearls is looking at removing the requirement for the bonus action altogether but doesn't want to just hand out a straight extra attack. I also liked a suggestion I read on using Str for the main hand weapon and removing the light requirement, then off-hand uses dex and must be light. This forces MAD (Multi-Attribute Dependency) but given Dex is often seen as too strong and Str is the second weakest stat after int it is a way to bring balance. Unfortunately it hurts rangers because they also need wis for spells.

I like your ideas of giving bonuses to some of the side abilities and actions. Those have great flavor and are unlikely to be too strong.

Here's a couple good articles that might help you (especially the last one):
Action Economy in 5e (to help you understand why a bonus action is so expensive)
Understanding Two Weapon Fighting
Two Weapon Fighting Hacks
Comparing the Math of various changes to two weapon fighting (with interactive tool to test your ideas) vs other fighting styles