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Author Topic: Under the Hood: Great Weapon Master and Sharpshooter  (Read 5150 times)


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Under the Hood: Great Weapon Master and Sharpshooter
« on: October 25, 2015, 01:28:10 PM »
For the most part, Feats are nicely done in 5e. Players are no longer forced to review dozens of Feats as they create a character, no longer have to start setting up Feat chains at first level in order to get the desired Feat at 15th level, and generally don’t have to worry much about attribute and proficiency restrictions.
However, two feats have turned into “no brainers”: Great Weapon Master, and Sharpshooter. The former seems to be used by every heavy weapon user at my table, and the latter by every character using primarily ranged weapons. Both grant great “passive” abilities, either bonus “cleave” style attacks for the former, or effectively bonuses to hit for the latter.
Both also have a bonus, optional ability of taking a -5 to hit penalty while simultaneously granting a +10 to damage. While the passive abilities are always good, always to be used, when should the optional ability be used?
It depends on both the expected damage the character will do with a weapon, and with the base (no penalty) chance to hit.
The following chart highlights the issue, for the following three cases:
Character A, using a maul or greatsword, with 18 strength (so, expecting 11 damage on a non-critical hit.)

Character B, using a longbow with 18 dexterity (expecting 8.5 damage)

Character C, using a short bow with 16 dexterity (expecting 6.5 damage)

The Base Roll is the roll on a D20 to hit, with not using the optional ability.

The numbers indicate expected damage in without/with format; “with” refers to taking the -5 penalty to hit with a +10 bonus to damage. I’m disregarding critical hits for base rolls below 15 , to simplify the calculations. Some of the calculations have been rounded.

Base RollABC
16-19** (see ** note)(see ** note)(see ** note)

*at a die roll of 15, I account for critical damage when using the optional ability, which is the same for all rolls higher than this.
**accounting for critical hits for both possibilities still leaves the optional ability inferior. For example, for scenario A, rolling a 19 leads to expected damage of 1.45/1.4. There’s sudden improvement when the character needs to roll a ‘natural’ 20, a critical hit, since the chance to hit is the same for both possibilities, but the optional ability grants +10 damage, effectively adding half a point of expected damage in all cases.

For example, a longbow using character with 18 Dex (column B) needing a 9 or better to hit will expect to deal 5.1 points of damage if he just rolls, but expects to deal 6.5 points of damage if he takes a -5 to hit with a +10 to damage.
Note also for the very high probability of hitting rolls, the optional ability is much more effective than in more typical attacks, increasing expected damage by around 50% when a “2 or better” is needed…not that this comes up much in 5e.

As the reader can see from the chart, a heavy weapon user should take the penalty to hit/bonus to damage if he needs to roll a 10, or a lower number, to hit (without the penalty)—he’ll expect to deal more damage in this case. As soon as the heavy weapon user needs to roll an 11, he’s now (slightly) hurting his expected damage output by using the ability, and it only gets worse for even higher rolls. I’ve included an extra decimal place of accuracy at the key value where using the optional ability is mathematically inferior. So, the big weapon user won’t use the optional ability if he needs an 11 or better to hit.

On the other hand, a longbow user won’t use the ability whenever he would normally need a 12 or higher to hit.

Finally, the not particularly powerful shortbow user won’t use the ability whenever he would hit on a 13 or higher roll.

This establishes the trend: as your expected damage gets higher, the optional ability won’t get used as you need ever lower rolls.

This might seem like the usefulness of the optional feat drops off, but the roll for the cutoff doesn’t get lower very quickly. For example, a character with an expected damage of 20 (dealing, say, 4d6 + 6 heavy weapon damage, about as high as it gets on a single typical hit, and almost double case A, above) will do the same expected damage whether he uses the ability or not when he needs to roll a 6 or better1—he shouldn’t use the ability if he needs to roll a 7 or better to hit. This may seem like the ability will become less useful, but in practice not so, because that kind of damage output would only come at high levels. At low levels needing to hit on a 6 (or lower) roll isn’t very likely, but it’ll be  more likely against 5e’s monsters as the character gains levels, as monster armor doesn’t improve nearly as rapidly with challenge rating compared to characters’ proficiency bonus and ability modifiers (especially compared to the previous two editions of the game).

Damage is hard to improve significantly, so far more worth noting is that as a character’s bonuses to hit improves (relative to monster armor class), he’ll need lower and lower to-hit rolls even if his damage doesn’t improve…and so again the “optional” ability will become more and more useful as the character gains levels, at least when fighting relatively weak monsters. Even many boss monsters don’t really have the AC to justify not using the ability. For example, a Beholder has an AC 18, and challenge rating of 13. A level 13 greatsword wielder (with expected damage of 11) could easily need only an 9 or better to hit that (+5 proficiency, +4 from Strength, for example, with plenty of ways to get a bigger bonus).
So, the optional ability of these feats is good at low level, with a bit of discretion on use. This discretion becomes less and less necessary as the character gains levels.

1.   I’ll leave this calculation as an exercise for the interested reader. Note that if you include critical hit damage for both possibilities, the expected damage will increase the same amount for both.

Bloody Stupid Johnson

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Under the Hood: Great Weapon Master and Sharpshooter
« Reply #1 on: October 30, 2015, 08:01:07 PM »
Well its interesting. I haven't seen a Great Weapon user in play as yet myself.
The numbers seem to show its pretty good, but I don't think quite to the point of eclipsing other options (by comparison just a STR increase at 11-or-better to hit would be +0.5 damage for the increase in damage bonus, plus 5% of whatever the normal damage roll is).
A couple of other points about Great Weapon Fighting:
*I imagine fairly often even low-level characters would end up with Advantage and thus get to the equivalent of '6 or better to hit' though (an 11 or more, or 50% chance, would become 75% for two rolls, equivalent to rolling over a 5).

*it actually seems like a quite well-designed feat in that it works in a variety of circumstances. If it was just a damage bonus then it could be 'nerfed' by using bunches of low-HP monsters against whom the damage bonus is irrelevant (since a normal hit without it would take them out) but thanks to the passive "Cleave" type ability, that doesn't work. (Sharpshooter isn't quite as good because the passive ability isn't there).


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Under the Hood: Great Weapon Master and Sharpshooter
« Reply #2 on: May 28, 2017, 02:45:57 AM »
That meshes more or less with my own calculations. Though I approached it from a different direction.

In my case I worked it out to a max stat of 20. Which a fighter PC using array or point buy can hit by level 6.

Things really jump up though if you factor in teamwork and advantage. As a player I try to set up flanking moves as much as can. Two rolls at penalty  instead of one.

Fighter Battle Master maneuvers that improve to-hit can also swing those feats even more.