How effective in combat regarding damage output could a Dexterity-based Barbarian be?

Question

The Barbarian is a MAD (Multiple Ability Dependent) class. They require a good Strength stat for their attacks, good Constitution due to their need for a large amount of HP, and good Constitution and Dexterity for a decent AC.

From their Rage class feature (PHB, p. 47):

• You have advantage on Strength checks and Strength saving throws.
• When you make a melee weapon attack using Strength, you gain a bonus to the damage roll [...]

And from their Reckless Attack class feature (PHB, p. 47):

When you make your first attack on your turn, you can decide to attack recklessly. Doing so gives you advantage on melee weapon attack rolls using Strength during this turn [...]

Also from their Unarmored Defense class feature (PHB, p. 47):

While you are not wearing any armor, your Armor Class equals 10 + your Dexterity modifier + your Constitution modifier.

And finally, their Danger Sense class feature (PHB, p. 47):

You have advantage on Dexterity saving throws against effects that you can see [...]

I've always been inclined to prioritise Strength and Constitution, treating Dexterity as their tertiary stat. But what about if Dexterity were their primary stat (or secondary with Constitution as their primary stat), with Strength being their tertiary (or an even lower priority) stat?

I want to optimise a Shadar-kai (PHB, p. 23 for base stats; MToF, p. 63 for subrace stats) Barbarian, who get racial bonuses of +2 to Dexterity and +1 to Constitution. Standard array or point buy. I want to put my best two stats in Dexterity and Constitution. No multiclassing or homebrew, but feats and Unearthed Arcana are OK (although I'd prefer no Unearthed Arcana if possible); hence this is not AL.

I'll assume no magic items for now (I don't want a build that is reliant on a magic item they might not have access to in play), and I'm focussing on Tier 2 levels (I'm reasoning that at Tier 1, everyone's weak anyway, and at Tiers 3-4, everyone is OP, especially if no-one has multiclassed). Also I have no party at the moment, so if that is important, assume the standard fighter, rogue, wizard, cleric with their simplest archetypes.

How could this character be effective in combat? What role could they fill? All I can think of is tank, probably with a shield and a rapier... Ideally, I'd like to optimise this character to deal as much damage as they can that does not rely on Strength, but without sacrificing their durability (AC, HP, etc) too much, since that's partly the point of sacrificing the high Strength score.

Answer 1

Your self-answer covers the standard approach well, so I'll take a stab at an alternate approach.

Dr. Hit-and-Run

Or: How I Learned to Stop Worrying and Love My Mom

Picture this: three frost giants bear down on a party of adventurers. The fighter chops away at the closest one's ankles while the rogue threads a shot between the gaps in their armor. The wizard wiggles her fingers and the giants' eyes glaze over. One swings its axe and barely misses its ally, another stares dumbly at its hands, and the final one flees. The fighter and rogue complain that the wizard should have cast fireball and wish that they had just brought along another rogue.

Wait. That's not what they would say. Without inflicting a single point of damage, the wizard completely changed the course of the fight. Damage is life, control is life insurance.

The Control Barbarian

Most Barbarian Paths focus on increasing personal defense (Bear Totem) or personal offense (Berserker). One, however, focuses on party defense: Ancestral Guardian. At Level 3, they receive the following feature (XGtE, p. 10; emphasis mine):

Ancestral Protectors

Starting when you choose this path at 3rd level, spectral warriors appear when you enter your rage. While you're raging, the first creature you hit with an attack on your turn becomes the target of the warriors, which hinder its attacks. Until the start of your next turn, that target has disadvantage on any attack roll that isn't against you, and when the target hits a creature other than you with an attack, that creature has resistance to the damage dealt by the attack. The effect on the target ends early if your rage ends.

Combat as a control-focused Ancestral Guardian starts out like most barbarians. You rage, run at the biggest monster on the battlefield, and try to hit it in the face. From then on, your allies will scratch their heads and wonder if their barbarian is broken.

Once you hit your target, they will be harassed by a wide array of terrifying creatures; your not-mad-just-disappointed mother, way-too-much-perfume aunt, and have-I-told-you-about-my-time-in-the-war grandfather, will unite to tell your enemy why they should attack you instead of your allies.

Now that your biggest opponent wants you deader than usual, it's time to beat a hasty retreat. The Mobile feat (PHB, p. 168) lets you leave their reach without provoking an opportunity attack. Use it to stroll on over (with +10 speed from Mobile and +10 speed from barbarian's Fast Movement) to some of your smaller enemies and remind them that you're still a barbarian.

Your other allies can now engage the target of your ancestors with near impunity. Even if the harassed creature manages to hit with disadvantage, your allies have resistance to its damage. Congratulations, you just turned your whole party into Bear Totem barbarians who took the Dodge action. If the creature instead decides to chase you (assuming it can compete with your 50' speed), your allies get free opportunity attacks.

The Melee Build

• Basic setup: Rapier and shield. Half-plate brings you up to AC 19, but you have AC 18 in your skivvies, so you might not need it.
• Initial stats: 16 DEX and 16 CON are the only requirements. I'd recommend 12 STR, so you're still a decent grappler with advantage from rage. You could technically dump it, though, if you want.
• Level 3: You get Ancestral Protectors. Without the Mobile feat, this isn't quite awesome yet. You can use a whip's reach to approximate the feat.
• Level 4: Build online. Grab the Mobile feat and run around stabbing anything that moves.
• Level 6: You get Spirit Shield, which prevents even more damage without using any resources.
• Level 8: +2 DEX. Your unarmored AC is now 17+2, so you can ditch the half-plate.
• Level 12: +2 DEX. Your unarmored AC now equals plate!

The Ranged Build

Ben makes a good point in the comments - since Ancestral Protectors works at range, you can make an entirely ranged character if you want.

Instead of a rapier and shield, you just need one hand crossbow. Grab the Crossbow Expert feat (PHB, p. 165) in place of Mobile to get an additional attack (except on rounds when you begin raging). That feat also removes the disadvantage from ranged attacks while you're in melee, allowing you to still run up and tank. Later on, you can grab the Sharpshooter feat (PHB, p. 170), particularly if your party is good at generating advantage. The question requested no multiclassing, but optimally you would dip a level of fighter for the Archery fighting style.

The only thing you really lose is your shield (since you need a free hand to reload the crossbow); in exchange, you gain an additional attack on most combat turns. If you need really long range, you can easily pull out a longbow.

My Experience

One of my current Adventurers League characters is an Ancestral Guardian / Battle Master using a Strength version of this build. When I originally wrote this answer, he was an Ancestral Guardian 7 / Battle Master 3. Since then, he has capped out at Ancestral Guardian 16 / Battle Master 4. He has been quite fun to play and is extremely effective at locking down big hitters.

(This is outside the scope of the question, but don't be afraid to make a strength-based Shadar-kai. Guess what the strength score of my strength-based 10th-level barbarian is? Did you guess 16? Don't tell anyone, but I never raised it!)

How effective is he, really? The short answer is the most convincing: a wizard, protected by ancestors, survives longer than the reckless-attacking barbarian. (You obviously won't be using Reckless Attack, but the numbers are still impressive.) What follows is a condensed version of the math from my answer to "Most effective way of improving survivability for an Ancestral Guardian Barbarian".

The PCs

Class	AC	Con	HP
Ancestral Guardian 5	19	+3	55
Champion Fighter 5	20	+3	49
Hunter Ranger 3 / Rogue 2	16	+2	42
Evocation Wizard 5	15	+1	27
Archfey Warlock 5	14	+2	38

The Monsters

This fight will be a Deadly encounter, as it is the boss fight. The PCs will face:

• One CR 5 Gladiator (MM, p. 346)
• Five CR 1 Duergar (MM, p. 122)

A fireball from the evocation wizard will seriously injure or kill several Duergar, leaving the rest for cleanup by the warlock and the ranger/rogue. With that in mind, let's focus on the Gladiator. The Gladiator attacks three times with a +7 to hit, each dealing 11 damage on average (18 on a crit).

The Numbers

As a baseline, the barbarian will last 4.4 rounds against the Gladiator while attacking recklessly, or 6.9 rounds normally.

Class	Base Rounds	Ancestors
Ancestral Guardian 5	4.4	—	Reckless
Champion Fighter 5	3.4	18.4
Hunter Ranger 3 / Rogue 2	2.0	7.0
Evocation Wizard 5	1.2	3.9	No shield
Archfey Warlock 5	1.6	4.7

The wizard can last around 5 rounds if they cast shield on the first two turns of the fight. The fighter survives more than 5 times longer than without ancestors!

Conclusion

Will your dexterity-based Ancestral Guardian barbarian top the DPS charts? Nope. Will your Ancestral Protectors feature draw envious looks from control wizards? Probably. Will you have a blast running laps around enemies while your mom nags them so hard they fail at their one job? Definitely.

Answer 2

I will have a go at answering my own question; starting with the stats (including the +2 to DEX and +1 to CON that Shadar-kai get) using the standard array (15, 14, 13, 12, 10, 8), we would have 16s in both DEX and CON (the 14 in DEX and the 15 in CON, both raised to 16 with the racial bonuses).

So my Unarmored AC will be 16 (18 with a shield) and my HP will be "12 + 3 = 15" (at level 1) + "7 + 3 = 10" (for each additional level; e.g. at level 5, my HP is 55).

I'm focusing on Tier 2 levels, meaning levels 5-10, so I will have Extra Attack and would have had two ASIs by level 10 (meaning up to two feats; see feats below).

Some things I have to accept are:

• Reckless Attack only benefits STR-based attacks and is effectively useless to this build; there's no compensation for this one, it's simply a waste of a class feature (so is Indomitable Might at level 18, and the +4 to STR from Primal Champion at level 20 is wasted as well, but they're not Tier 2 so are less relevant to this question).
• Rage is not useful offensively, since that only benefits STR-based attacks, so I have to accept that Rage is simply for damage resistance and other indirect benefits. Actually, that's not quite true...

Dealing more damage from Rage

One way to extract some more offensive use out of Rage is via some of the Barbarian archetypes. All of the archetypes grant some extra benefits to raging, involving increased durability or by imposing (dis)advantage, but some add directly offensive benefits (meaning ways to deal more damage) that do not rely on STR:

• Path of the Storm Herald has the Storm Aura feature (XGtE, p. 10) that allows you to deal extra damage when raging:

  Your aura has an effect that activates when you enter your rage, and you can activate the effect again on each of your turns as a bonus action.
  [...]
  Desert. When this effect is activated, all other creatures in your aura take 2 fire damage each. The damage increases when you reach certain levels in this class, increasing to 3 at 5th level, 4 at 10th level, 5 at 15th level, and 6 at 20th level.
  Sea. When this effect is activated, you can choose one other creature you can see in your aura. The target must make a Dexterity saving throw. The target takes 1d6 lightning damage on a failed save, or half as much damage on a successful one. The damage increases when you reach certain levels in this class, increasing to 2d6 at 10th level, 3d6 at 15th level, and 4d6 at 20th level.

• Path of the Zealot has the Divine Fury feature (XGtE, p. 11), which allows you to deal additional damage with weapon attacks that is not tied to STR-based attacks, since it doesn't mention STR in the description:

  While you're raging, the first creature you hit on each of your turns with a weapon attack takes extra damage equal to 1d6 + half your barbarian level.

• Path of the Berserker has the Frenzy feature (PHB, p. 49), allowing you to make an extra attack, thereby increasing your damage output:

  ... for the duration of your rage you can make a single melee weapon attack as a bonus action on each of your turns after this one.

Overall, given the drawbacks to the Frenzy feature due to the exhaustion side effects, and that the feats I discuss below include ways to gain an extra attack (which use up your bonus action), I'd say the Divine Fury feature is the most reliable and consistent damage output, since the others also use up your bonus action.

Using Feats to compensate

Certain feats would help to get more out of attacks that don't rely on STR. Firstly, the Great Weapon Master feat (PHB, p. 167) allows for an extra attack to be made on your turn if you crit or kill/knock out someone, and this counts for any melee weapon attack, even if it isn't a two-handed weapon:

• On your turn, when you score a critical hit with a melee weapon or reduce a creature to 0 hit points with one, you can make one melee weapon attack as a bonus action.

There's also the Dual Wielder feat (PHB, p. 165); even though dual weapon fighting isn't as strong as using two-handed weapons (there's at least one other question that goes into that), for a DEX based warrior it at least guarantees an extra attack per round (so long as we didn't need our bonus action for something else, such as raging), and the Dual Wielder feat helps make up the loss of the shield with +1 to AC. The feat also allows us to wield two rapiers, meaning we can keep those 1d8 + DEX weapon attacks:

• You gain a +1 bonus to AC while you are wielding a separate melee weapon in each hand.
• You can use two-weapon fighting even when the one-handed melee weapons you are wielding aren't light.

Finally, the Sentinel feat (PHB, pp. 169-170) allows for ways to use your reaction to make a melee weapon attack, thereby increasing your damage output:

• Creatures provoke opportunity attacks from you even if they take the Disengage action before leaving your reach.

• When a creature within 5 feet of you makes an attack against a target other than you (and that target doesn’t have this feat), you can use your reaction to make a melee weapon attack against the attacking creature.

By level 10, we can have two of these feats, so unless we just decide to increase our DEX scores, then I'd say Dual Wielder would maximise the number of attacks made, although if we really don't want to sacrifice even 1 point of AC, then Sentinel increases the chances of making another attack using your reaction.

It's never going to be competitive with STR-based Barbarians

Although there are a few ways to squeeze a little extra damage or extra attacks out of some rage abilities or feats, clearly their damage output is never going to match a STR-based barbarian, given that the Rage and Reckless Attack features benefit STR-based attacks, and that the damage output on a STR-based weapon is higher (see other question about TWF vs. GWF).

But, this build could at least hold their own, acting largely as a tank but being able to dish out up to three attacks with the right feats.