In Unearthed Arcana: Expert Classes, changes were made to the Great Weapon Master feat. How does this affect the damage output of Great Weapon Users?

Question

On September 29th, 2022, Playtest material for OneD&D was released for the Expert Class Groups, and included in this unearthed arcana were some planned feats for the new version of Dungeons and Dragons, including revised versions of feats that exist in 5th Edition D&D.

Notably, the Great Weapon Master feat was changed: the option to lower the attack roll of an attack in exchange for drastically improved damage if the attack connects was removed, and replaced with a flat damage bonus that can be applied to one of the attack rolls made in a single turn.

Great Weapon Master feat

^{As featured in the 2014 Player's Handbook for 5th Edition D&D on page 167}

Before you make a melee attack with a heavy weapon that you are proficient with, you can choose to take a -5 penalty to the attack roll. If the attack hits, you add +10 to the attack's damage.

Great Weapon Master feat

^{As featured in the 2022 Unearthed Arcana OneD&D Playtest: "Expert Classes"}

Heavy Weapon Mastery. When you hit a creature with a Heavy Weapon as part of the Attack Action on your turn, you can cause the weapon to deal extra damage to the target. The extra damage equals your Proficiency Bonus, and you can deal it only once per turn.

How does this change affect the damage output of a character that uses Heavy Weapons?

Answer 1

Long Story Short: The new Feat is actually stronger at most levels of play

As expected, the higher the Armor Class of the target, the worse the older GWM feat is, and the better the newer GWM feat is. So the determining factor is at what Armor Classes the new feat "breaks even".

What we find, if we look at the numbers, is that the break-even point for each level occurs at surprisingly low Armor Class values, and this remains true for most levels of play.

Assumptions and Scenario

We will first need to make a few assumptions, to have controllable variables.

First, we will assume that we are working with a fighter, at various levels between level 1 and 20. She takes the Great Weapon Fighting Style (reroll damage roll dice that roll a 2 or lower), uses a Greatsword, and has a 17 in Strength at level 1.

In D&D 5e, she is a variant human that takes the Great Weapon Master feat at level 1, and then takes Strength ASIs at levels 4 and 6 to get to 19 and 20 strength, respectively, at those levels.

In OneD&D, she takes the Great Weapon Master feat at level 4, which bumps her strength up to 18, and then takes the Ability Score Increase feat at level 6 to increase her strength to 20.

In both versions, we assume she is fighting a single enemy creature with infinite Hit Points. This means that the only way to gain the Bonus Action attack is to deal a critical hit. We are going to ignore Subclass features, and use the features of the baseline PHB2014 Fighter class.

Directly Comparing the Damage

Running these stats through a probability calculator, we arrive at the following table of average Damage per Round (DPR) that our fighter deals at her level. Since these values depend heavily on the armor class of her opponent, we add columns that adjust for varying Armor Class values, ranging from 0 (i.e. we assume she lands every single hit that isn't a natural 1) to 25 (i.e. the highest unmodified armor class of any statted creature in 5th Edition D&D, which we are using because OneD&D does not have any discrete creature blocks yet).

I've removed any rows that aren't accessible (for example, the new fighter cannot gain any Great Weapon Master features until level 4) or where the level change had no effect (there is no numerical change to damage output between levels 1 to 2, for example).

Armor Class columns are limited due to the formatting limitations on this website, as adding more would push the table off the page, so looking at a total range of possible Armor Class values, I've truncated the list down to just the thresholds at which the Armor Class actually swings the delta from the old feat to the new feat (or vise-versa), which starts at Armor Class 14 and goes up. Below Armor Class 14, the old feat always has higher damage output, and above Armor Class 18, the new feat always has higher damage output. In between, depends on the level of the character.

"Adv" stands for Advantage, "Dis" stands for Disadvantage. "w/feat" means the feat was taken, but only the Bonus Action attack is being used (if permitted by the rolls), not the extra damage, which applies only to the old feat (because there is no opportunity cost for using the bonus damage with the new feat).

	AC 13	AC 14	AC 15	AC 16	AC 17	AC 18	AC 20
Level 1 Greatsword	7.783	7.217	6.650	6.083	5.517	4.950	3.817
Level 1 Greatsword Adv	10.758	10.332	9.851	9.312	8.717	8.066	6.593
Level 1 Greatsword Dis	4.809	4.101	3.449	2.854	2.316	1.834	1.041
Level 1 Greatsword w/feat	8.172	7.577	6.982	6.388	5.793	5.197	4.008
Level 1 Greatsword w/feat Adv	11.806	11.340	10.811	10.220	9.567	8.852	7.235
Level 1 Greatsword w/feat Dis	4.821	4.111	3.458	2.861	2.322	1.839	1.043
Level 1 Greatsword OldGWM	9.398	8.277	7.157	6.037	4.918	3.797	1.558
Level 1 Greatsword OldGWM Adv	15.876	14.413	12.833	11.135	9.321	7.389	3.175
Level 1 Greatsword OldGWM Dis	3.443	2.641	1.946	1.358	0.876	0.502	0.074
Level 4 Greatsword	9.050	8.433	7.817	7.200	6.583	5.967	4.733
Level 4 Greatsword Adv	12.036	11.635	11.172	10.648	10.062	9.415	7.935
Level 4 Greatsword Dis	6.064	5.232	4.461	3.752	3.104	2.518	1.532
Level 4 Greatsword w/feat	9.502	8.855	8.207	7.560	6.912	6.265	4.970
Level 4 Greatsword w/feat Adv	13.209	12.769	12.262	11.687	11.044	10.333	8.709
Level 4 Greatsword w/feat Dis	6.079	5.245	4.472	3.761	3.112	2.525	1.535
Level 4 Greatsword OldGWM	10.990	9.818	8.645	7.473	6.300	5.128	2.783
Level 4 Greatsword OldGWM Adv	17.988	16.579	15.047	13.392	11.615	9.716	5.549
Level 4 Greatsword OldGWM Dis	4.555	3.603	2.764	2.036	1.420	0.916	0.245
Level 4 Greatsword NewGWM	10.902	10.155	9.408	8.660	7.912	7.165	5.670
Level 4 Greatsword NewGWM Adv	15.029	14.524	13.942	13.282	12.544	11.728	9.864
Level 4 Greatsword NewGWM Dis	7.059	6.090	5.192	4.366	3.612	2.930	1.780
Level 5 Greatsword	19.333	18.100	16.867	15.633	14.400	13.167	10.700
Level 5 Greatsword Adv	24.750	24.072	23.270	22.345	21.297	20.125	17.412
Level 5 Greatsword Dis	13.917	12.128	10.463	8.922	7.503	6.208	3.988
Level 5 Greatsword w/feat	19.938	18.688	17.436	16.180	14.922	13.660	11.128
Level 5 Greatsword w/feat Adv	26.032	25.351	24.543	23.609	22.545	21.351	18.566
Level 5 Greatsword w/feat Dis	13.942	12.151	10.484	8.940	7.519	6.222	3.998
Level 5 Greatsword OldGWM	24.035	21.744	19.448	17.146	14.838	12.525	7.882
Level 5 Greatsword OldGWM Adv	37.265	34.861	32.215	29.321	26.178	22.779	15.197
Level 5 Greatsword OldGWM Dis	11.233	9.107	7.205	5.526	4.071	2.840	1.049
Level 5 Greatsword NewGWM	22.750	21.418	20.068	18.701	17.314	15.910	13.048
Level 5 Greatsword NewGWM Adv	29.020	28.326	27.498	26.532	25.422	24.164	21.177
Level 5 Greatsword NewGWM Dis	16.367	14.371	12.483	10.711	9.060	7.534	4.881
Level 6 Greatsword	22.167	20.833	19.500	18.167	16.833	15.500	12.833
Level 6 Greatsword Adv	27.225	26.625	25.892	25.025	24.025	22.892	20.225
Level 6 Greatsword Dis	17.108	15.042	13.108	11.308	9.642	8.108	5.442
Level 6 Greatsword w/feat	22.832	21.484	20.134	18.780	17.422	16.062	13.331
Level 6 Greatsword w/feat Adv	28.605	28.004	27.267	26.394	25.384	24.234	21.509
Level 6 Greatsword w/feat Dis	17.137	15.069	13.133	11.331	9.661	8.126	5.454
Level 6 Greatsword OldGWM	27.461	25.073	22.679	20.280	17.875	15.464	10.624
Level 6 Greatsword OldGWM Adv	41.119	38.857	36.345	33.580	30.557	27.272	19.898
Level 6 Greatsword OldGWM Dis	14.188	11.734	9.513	7.526	5.772	4.252	1.913
Level 6 Greatsword NewGWM	25.712	24.297	22.864	21.412	19.942	18.454	15.423
Level 6 Greatsword NewGWM Adv	31.601	30.992	30.243	29.349	28.307	27.111	24.235
Level 6 Greatsword NewGWM Dis	19.749	17.494	15.353	13.330	11.433	9.666	6.546
Level 9 Greatsword	23.500	22.167	20.833	19.500	18.167	16.833	14.167
Level 9 Greatsword Adv	27.692	27.225	26.625	25.892	25.025	24.025	21.625
Level 9 Greatsword Dis	19.308	17.108	15.042	13.108	11.308	9.642	6.708
Level 9 Greatsword w/feat	24.176	22.832	21.484	20.134	18.780	17.422	14.698
Level 9 Greatsword w/feat Adv	29.072	28.605	28.004	27.267	26.394	25.384	22.943
Level 9 Greatsword w/feat Dis	19.339	17.137	15.069	13.133	11.331	9.661	6.723
Level 9 Greatsword OldGWM	29.843	27.461	25.073	22.679	20.280	17.875	13.047
Level 9 Greatsword OldGWM Adv	43.134	41.119	38.857	36.345	33.580	30.557	23.721
Level 9 Greatsword OldGWM Dis	16.876	14.188	11.734	9.513	7.526	5.772	2.965
Level 9 Greatsword NewGWM	28.086	26.672	25.234	23.774	22.290	20.782	17.698
Level 9 Greatsword NewGWM Adv	33.070	32.599	31.988	31.235	30.334	29.281	26.693
Level 9 Greatsword NewGWM Dis	23.031	20.619	18.303	16.093	13.997	12.023	8.473
Level 11 Greatsword	35.250	33.250	31.250	29.250	27.250	25.250	21.250
Level 11 Greatsword Adv	41.538	40.837	39.938	38.837	37.538	36.038	32.438
Level 11 Greatsword Dis	28.962	25.663	22.562	19.663	16.962	14.463	10.062
Level 11 Greatsword w/feat	35.939	33.937	31.934	29.928	27.919	25.907	21.870
Level 11 Greatsword w/feat Adv	42.919	42.220	41.322	40.224	38.925	37.426	33.821
Level 11 Greatsword w/feat Dis	28.995	25.694	22.593	19.692	16.990	14.487	10.082
Level 11 Greatsword OldGWM	44.374	40.845	37.307	33.761	30.206	26.639	19.473
Level 11 Greatsword OldGWM Adv	63.597	60.617	57.281	53.585	49.524	45.093	35.081
Level 11 Greatsword OldGWM Dis	25.306	21.276	17.596	14.266	11.286	8.657	4.448
Level 11 Greatsword NewGWM	39.925	37.905	35.871	33.820	31.747	29.651	25.370
Level 11 Greatsword NewGWM Adv	46.918	46.220	45.321	44.221	42.918	41.410	37.759
Level 11 Greatsword NewGWM Dis	32.910	29.508	26.258	23.161	20.219	17.439	12.394
Level 13 Greatsword	37.250	35.250	33.250	31.250	29.250	27.250	23.250
Level 13 Greatsword Adv	42.038	41.538	40.837	39.938	38.837	37.538	34.337
Level 13 Greatsword Dis	32.462	28.962	25.663	22.562	19.663	16.962	12.162
Level 13 Greatsword w/feat	37.939	35.939	33.937	31.934	29.928	27.919	23.890
Level 13 Greatsword w/feat Adv	43.418	42.919	42.220	41.322	40.224	38.925	35.725
Level 13 Greatsword w/feat Dis	32.496	28.995	25.694	22.593	19.692	16.990	12.185
Level 13 Greatsword OldGWM	47.897	44.374	40.845	37.307	33.761	30.206	23.062
Level 13 Greatsword OldGWM Adv	66.223	63.597	60.617	57.281	53.585	49.524	40.282
Level 13 Greatsword OldGWM Dis	29.685	25.306	21.276	17.596	14.266	11.286	6.377
Level 13 Greatsword NewGWM	42.934	40.922	38.897	36.855	34.793	32.704	28.435
Level 13 Greatsword NewGWM Adv	48.418	47.918	47.220	46.320	45.220	43.916	40.684
Level 13 Greatsword NewGWM Dis	37.461	33.888	30.461	27.174	24.028	21.027	15.488
Level 17 Greatsword	39.250	37.250	35.250	33.250	31.250	29.250	25.250
Level 17 Greatsword Adv	42.337	42.038	41.538	40.837	39.938	38.837	36.038
Level 17 Greatsword Dis	36.163	32.462	28.962	25.663	22.562	19.663	14.463
Level 17 Greatsword w/feat	39.939	37.939	35.939	33.937	31.934	29.928	25.907
Level 17 Greatsword w/feat Adv	43.717	43.418	42.919	42.220	41.322	40.224	37.426
Level 17 Greatsword w/feat Dis	36.196	32.496	28.995	25.694	22.593	19.692	14.487
Level 17 Greatsword OldGWM	51.414	47.897	44.374	40.845	37.307	33.761	26.639
Level 17 Greatsword OldGWM Adv	68.498	66.223	63.597	60.617	57.281	53.585	45.093
Level 17 Greatsword OldGWM Dis	34.413	29.685	25.306	21.276	17.596	14.266	8.657
Level 17 Greatsword NewGWM	45.938	43.933	41.919	39.889	37.840	35.766	31.523
Level 17 Greatsword NewGWM Adv	49.717	49.418	48.918	48.220	47.320	46.219	43.402
Level 17 Greatsword NewGWM Dis	42.190	38.455	34.867	31.414	28.091	24.896	18.914
Level 20 Greatsword	52.333	49.667	47.000	44.333	41.667	39.000	33.667
Level 20 Greatsword Adv	56.450	56.050	55.383	54.450	53.250	51.783	48.050
Level 20 Greatsword Dis	48.217	43.283	38.617	34.217	30.083	26.217	19.283
Level 20 Greatsword w/feat	53.022	50.356	47.691	45.025	42.358	39.691	34.350
Level 20 Greatsword w/feat Adv	57.829	57.430	56.764	55.833	54.634	53.170	49.443
Level 20 Greatsword w/feat Dis	48.250	43.317	38.650	34.250	30.116	26.248	19.311
Level 20 Greatsword OldGWM	68.187	63.514	58.837	54.155	49.466	44.769	35.341
Level 20 Greatsword OldGWM Adv	90.545	87.515	84.018	80.054	75.621	70.719	59.485
Level 20 Greatsword OldGWM Dis	45.871	39.569	33.732	28.361	23.457	19.018	11.541
Level 20 Greatsword NewGWM	59.022	56.356	53.688	51.015	48.335	45.642	40.197
Level 20 Greatsword NewGWM Adv	63.829	63.430	62.764	61.833	60.634	59.170	55.439
Level 20 Greatsword NewGWM Dis	54.250	49.309	44.614	40.149	35.896	31.842	24.305

Observations

It's clear from initial observation that the new feat is better than the old feat in most combat situations.

In the levels 1-3 range, the old feat is obviously better just because the new feat isn't even obtainable yet, since it has a level 4 prerequisite. So the old feat (obtainable at level 1) dominates for several levels uncontested.

Once we get to level 4, though, things change. We see that at AC 13, we see that the old feat is better (10.990→10.902 for a -0.801% decrease), but at AC 14, the new feat is better (9.818→10.155 for a 3.432% increase). In my experience as DM, by this point in the game, a player should reasonably expect an enemy creature to have an armor class of around 14-16, with higher or lower values tending to be outliers—Armor Classes lower than 14 tend to be trivial, filler creatures that aren't meant to threaten the party, and Armor Classes higher than 16 tend to be boss monsters or unusual, non-typical encounters.

Levels 5-6 see some power increase for the older version of the feat, since the extra attack, proficiency increase, and (at level 6) strength increase scale better for the old version of the feat than they do for the newer version. This makes sense: a flat damage increase to one attack isn't going to scale as well as to-hit & damage increases to multiple attacks, and the +to-hit for old GWM is more powerful than the +to-hit for new GWM. But, even at these levels, Armor Class 15 continues to be better for the new feat than the old feat (19.448→20.068 for a 3.188% improvement). And it'll continue to be better all the way up to level 10.

Level 11, with the third [baseline] attack, is where the new feat finally falls behind the old feat for Armor Class 15 (37.307→35.871 for a -3.849% decrease). But at this point, the new feat is still ahead for Armor Class 16 (33.761→33.820 for a 0.175% increase), and at this point in the game, the average armor class of enemy creatures ought to have gone up. Armor Class 16 is very typical for challenging encounters at level 11, and can often go as high as 18 or 20 depending on circumstances, while lower ACs are very rare.

At level 13, the improved proficiency bonus benefits the old feat more than the new one, so now the new Armor Class threshold is 17 (33.761→34.793 for a 3.057% increase), not 16 (37.307→36.855 for a -1.212% decrease). At this level one could argue that a character would rather have the old feat if the DM prefers lower armor class creatures. But as Armor Classes are going to continue to go up for the rest of Tier 3, that will cease to be the case.

Finally, only at level 20, does the threshold finally go up to Armor Class 18 (44.769→45.642 for a 1.950% increase). At a point in the game where PCs are expected to take on endgame challenges and gods whose Armor Class will rarely, if ever, dip below 20.

The facts are very clear: there are some encounter scenarios where the old feat would provide higher damage output overall, but those scenarios tend to involve disproportionately low Armor Class creatures that the party is unlikely to find challenging to begin with.