What are the mechanical consequences of adding the Two-Weapon Fighting fighting style to the benefits of the Dual Wielder feat?

Question

I've been reviewing the Two-Weapon Fighting information, and I don't understand why Dual Wielder doesn't grant a benefit like the Two-Weapon Fighting fighting style does.

The description of the feat says "you have mastery over fighting with two weapons", which implies that you would have already benefited from the two-weapon fighting style considering you've "mastered fighting with two weapons".

According to this thread "Is the Polearm Master Feat compatible with the Two-Weapon Fighting style?", a feat like Polearm Master basically adds the ability modifier to the offhand attack's damage inherently. Aside from limiting the damage of the offhand attack to a d4 of damage, I don't see why a whole feat like Dual Wielder wouldn't offer the same. Of course, I could be overlooking something that makes adding the benefit of the fighting style to the feat problematic.

What are the mechanical consequences of adding the Two-Weapon Fighting fighting style's benefit as an additional benefit of the Dual Wielder feat?

Answer 1

It would be overpowered compared to other Feats

The ability to attack more often is one which is highly sought after by the martial classes. As such, there are several Feats which give martial characters access to attacks via bonus actions. But while these Feats enable characters to attack more often, each of them also reduces the effectiveness of one or more of the character's attacks.

For example:

Polearm Master allows you to attack with the opposite end of a polearm with a bonus action

• BUT it requires you to use a less damaging weapon than other heavy weapons for your normal attacks (1d10 max, vs 2d6 max, for an average of 5.5 vs 7 per attack) and only gives you a 1d4 damage die for the bonus action attack (2.5+Ability average damage vs 7+Ability).

Crossbow Expert gives you a ranged bonus action attack.

• BUT it requires you to be attacking with a light weapon (often a hand crossbow), and only lets you use the hand crossbow for the bonus action attack. That means you'll be doing 1d6+Ability damage for all your attacks, rather than 1d10+Ability (or 1d8+Ability if you aren't proficient in heavy crossbows), for an average of 3.5+Ability vs 5.5+Ability per attack.

Dual Wielder lets you use more damaging weapons for two weapon fighting, increasing your damage for each attack.

• BUT you don't add your Ability modifier to the damage done by your bonus action attack, and one handed weapons do less damage than two handed weapons.

The give and take in each Feat keeps the elements balanced. Certain classes can make the two weapon fighting option more viable with Fighting Styles that accommodate it, but those classes are designed to be able to make one style of martial combat objectively better than other options for themselves (by making it do more damage, or hit more often). If you were to add the Ability bonus to the second weapon's attack via this Feat, it would make the Feat objectively better than other Feats that boost a martial class. It would be like rewriting the Crossbow Expert Feat to give a +2 to attack rolls made with crossbows weapons in addition to all its other benefits.

Answer 2

Well, repeating what Gandalf said, but comparing to the two strongest DPR feats we have, which are Polearm Master and GWM. Also, with math.

The feat becomes really strong - not completely broken though.

Without the feat, you would be doing 2d6 + Modifier, which at low levels (i.e. \$<4\$) means 2d6 + 3. With the feat, this increases to 2d8 + 6, which is a +5 damage on hit bonus, or \$+5 \cdot P\$, where \$P\$ is the probability to hit, increase on your average damage.

For reference, let's compare it to the other mentioned feats. Let's say you are fighting against an enemy with AC 13, which is the default value for low levels and a quite common number. Assuming you are using a Greatsword with Great Weapon Fighting (optimal damage), GWM increases your average damage by around 1.6 at no cost. Polearm Master increases your average damage by 2.2 - at the cost of a bonus action.

Your feat increases 2.85 at no cost. You could think "Oh but you use the bonus action" - but actually, you would already be using the bonus action if you were fighting with two weapons. The feat itself has no cost.

Against some other creatures, like a Zombie with 8 AC, your feat still gives a +4, while GWM gives +4.4 and Polearm Master a +3.2. Note that, again, Polearm Master has a cost, and GWM is specifically good against lower AC enemies. Against an enemy with Splint (17 AC), your feat gives +1.85, polearm +1.44 and it's better to not use GWM. Point being: your feat became competitive with the strongest DPR feats we have for melee, arguably outclassing both due to having no cost and being more versatile since it doesn't suck against high AC enemies. Sure, polearm master gives you reach and the better Opportunity Attack, but the feat provided a greater DPR increase than Polearm Master.

The reason I say it's not completely broken is just because the DPR increase will fade away as levels go up and extra attacks become more common, magic items become common but not enough for you to have two +X weapons probably, while GWM will just get stronger, and Polearm Master will probably be combo'd with Sentinel or a Cavalier archetype for a Defender-style play, or actually Polearm Master will be used WITH GWM.

But now my major point:

The fighting style becomes useless.

Both Polearm Master and GWM usually go with GWF for damage optimization. With your feat, you could dual wield without actually taking Two Weapon Fighting. This is the major problem. You would probably take defense and get a free +1 AC for that. Usually, homebrewing something that completely overlaps and overshadows another feature - in this case, the TWF fighting style - is bad design. You could change TWF in order to make it useful again, or you could stack the modifier bonus (please don't), but that's probably going too far.