What imbalance might arise from this alteration to the two-weapon fighting style?

Question

It's generally accepted that the two-weapon fighting style is considered a subpar option. It's disappointing when going by the numbers, the mechanics (just add a small bonus to your one extra attack), and the flavor (it's boring to imagine).

By far the biggest problem is that it doesn't scale. It's ahead for level 3-4, but once you hit level 5 and get your extra attack with fighter, you quickly start falling behind things like Great Weapon Fighting. Mileage against other fighting styles may vary, and while adding in feats like Dual Wielder can help, those other fighting styles have feats as well that negate any attempt to close the gap. All things considered, the two-weapon fighting style just feels and behaves lackluster, and it's turned many away from using it simply because what little flair it gives is not worth the penalties.

So one solution we've been considering at our table to counter that problem is to change the way the two-weapon fighting style itself works. This effect of this change would only be made in relation to extra attacks, keeping all else the same. The original style is written as such:

Two-Weapon Fighting

When you engage in two-weapon fighting, you can add your ability modifier to the damage of the second attack.

Under the revision we're considering, this would instead be written as:

Two-Weapon Fighting (Revised)

When you engage in two-weapon fighting, you can add your ability modifier to the damage of the second attack. Alternatively if you can make an extra attack, you can instead choose to make a number of offhand attacks up to the number of attacks that you take that turn, but without adding your ability modifier to their damage. Opportunity attacks may also add the damage dice from the offhand weapon to the attack.

All in all as I currently see it, this is finally a TWF I'd enjoy playing, and would consider on par in consideration with GWF or Dueling styles, with character style being the deciding factor instead of raw numbers.

So my question is: is there anything I'm missing here that would make this too overpowered or broken?

Answer 1

Providing additional attacks is a big problem

While the damage outputs are approximately the same for most levels using the revised option, other damage modifiers make the multiple attacks much much better. For example, a +1 magic weapon with the revised Two-Weapon Fighting gets an additional damage, but that is the smallest example.

Additional attacks also increases your effective critical hit chance. The 1d6 shortsword damage also has a 5% chance of being 2d6 (or a higher chance for a Champion fighter). This makes the damage no longer approximately equal to the proficiency bonus of +3. This is especially true when combined to some other features like Half-Orc racial traits and Barbarian features that make critical hits even more effective.

The most egregious example of abuse comes from spell enhancements. Spells like elemental weapon or shillelagh (for a multiclassed character) get compounded an additional time by this modification. When the fighter starts getting even more attacks at higher levels, it only gets worse.

Also, what about other sources of additional attacks

It is also unclear if the feature only applies to additional attacks gained from Extra Attack or also features like the Warlock invocation Lifedrinker. Do you get an additional bonus action attack when you attack using the haste spell? Consider using language that could not be conflated with the Extra Attack feature.

Answer 2

Your math is leading you to some inaccurate conclusions

In your calculations of the damage done by the two styles, you've made an understandable, but mistaken, decision at higher levels to multiply the damage done by a fighter using Great Weapon Fighter and Great Weapon Master 3/4. For example, you calculated the GWF/Greatsword(GWM) at 20th level as:

2d{1..6,3..6}+5)*4+40)*3/4+2d6

I'm not sure what the +2d6 at the end is about (since the fighter can't make an "off hand" attack as a bonus action while wielding a greatsword), but let's focus on the *3/4 part.

It's very reasonable for you to have made this adjustment based on the Great Weapon Master attack roll modifier: after all, a -5 seems to suggest that you'll have a 1/4 lower chance of hitting the target, since 5 is a quarter of 20 and a d20 roll determines your attack's success.

The problem with this calculation is that it assumes the probability of hitting an enemy without this -5 modifier is 100%! While characters at level 20 are indeed truly mighty, they are not usually fighting creatures which they are absolutely assured they will strike. A level 20 character will have an attack modifier of at least +11, often higher. But it's extremely unlikely they'll find themselves fighting foes with AC 12 or lower.

Since all of your damage calculations are done without adding damage modifiers for magical weapons, a more likely probability of a hit for a level 20 character might be 75% (hitting on a 6 or better). If you will normally hit on a 6 or better, a -5 to your attack roll means you now hit on an 11 or better, so your to-hit probability has gone from 75% to 50%. That means your expected damage has been multiplied by x where:

.75*x = .5

x = .5/.75= 2/3

Let's see what this does to your calculated average damage:

• Average damage TWF Longswords (standard) level 20: 47.5
• Average GWF Greatsword level 20: 76*2/3 = 50.666...
  • (47.5 and 76 gotten from provided anydice link)

And if I am correct that the +2d6 in the original calculation of GWF average damage is an error, the GWF average becomes even closer, to (76 - 7)*2/3 = 46

Either way, the true expected difference in damage per round is less than 2.5 damage points at level 20, rather than the 19.5 points gap you had calculated.

Given that the damage outputs at 20th level are more balanced than you previously thought, consider how your proposed change unbalances the system. Especially consider the fact that if a player will hit less than 75% of the time normally (such as if they hit on an 11 or better), the expected damage done by GWM will be even lower if you take the -5 to hit.

Naturally, you can't be exactly sure what your to-hit probability will be, or even what your average one will be (it will depend on your DM). But the calculations you're doing at higher level paint a picture of a combat scenario which will very rarely happen.

Answer 3

Comparison to Great Weapon Fighting

Here's a rough damage spread comparing Great Weapon Fighting, Two-Weapon Fighting, and TWF(Revised) styles at levels 3, 5, 11, and 20, as well as how damage might look when combined with either the Great Weapon Master or Dual Wielder feats at level 20 (changes TWF from shortswords to longswords). This doesn't account for things like crits, magic weapons, or hit probability, except a small rough adjustment to GWF with GWM at level 20.

The end result appears to be that TWF with extra attacks becomes more on par with GWF for damage, but spreads it out over more attacks. GWF still does better on average due to re-rolls, while TWF is more likely to get at least one hit in on an encounter. This comes at the cost of burning the bonus action every round, no free hand for spellcasting, and requiring more time to draw and stow to become fully engaged in combat. Dual Wielder negates that last drawback alongside increasing damage die to d8's with two longsword, but simple projections put this again roughly on par with the increased damage options offered by Great Weapon Master.

The biggest area of potential imbalance I currently see is in the number of attacks being made. As I see it though, the benefit is circumstantial to situations where there are a large number of weaker enemies (eg. Twig Blights), or where simply getting a hit is enough (eg. Mobile feat disengage). I can also see there also being concern for how roll heavy it might feel, but barring limited use action surge, that only really starts to come about at higher levels (6 attacks at lv11 (12 w/ AS), 8 attacks at lv20 (16 w/ AS)), but even then there are strategies to expedite the rolling process, and it doesn't get excessive until end game (and even then, twice a rest at absolute most).