DPS Stance
Overview
Both 
tanks and 
healers had actions that could sacrifice some of their utility to deal additional damage. These actions were referred to as "stances" as their status effects lasted indefinitely, and could be toggled off. DPS stance for healers were removed in Stormblood, and DPS stances for tanks were removed in Shadowbringers to streamline gameplay and enmity management.
Tanks
Tanks originally had two "stances" - one that increased enmity generated, reduced damage taken, but reduced outgoing damage (colloquially referred to as "tank stance"), and another that granted no extra enmity or damage reduction, but increased outgoing damage ("DPS stance"). Tanks at the time had to swap back-and-forth between the stances (called "stance dancing") in order to maximize DPS without losing aggro on the enemies. These stances for each jobs in their Stormblood instance are listed below:
| Stance |  Paladin |
 Warrior |
 Dark Knight
|
|---|---|---|---|
| Tank Stance | Shield Oath Reduces damage taken by 20%. Reduces damage dealt by 15%. Increases enmity generated. |
Defiance Increases maximum HP by 25%. Reduces damage dealt by 20%. Increases HP restored via healing magic by 20%. Using certain actions will increase the Beast Gauge, which increases parry rate by up to 10%. Beast Gauge is halved when swapping to Deliverance. Increases enmity generated. |
Grit Reduces damage taken, and damage dealt by 20%. Increases enmity generated. |
| DPS Stance |  Sword OathIncreases the potency of auto-attacks by 75. |
Deliverance Increases damage dealt by 5%. Using certain actions will increase the Beast Gauge, which increases critical hit rate by up to 10%. Beast Gauge is emptied upon Deliverance expiring. |
Darkside Increases damage dealt by 20%. MP no longer recovers passively or through other players, and can only be restored upon using certain actions. |
As each tank's abilities worked differently, so the degree to which one job needed to "stance dance" and in what situation varied between them. Paladin's and warrior's stances were mutually-exclusive, meaning they could not be active at the same time. Notably, dark knight's stances, Darkside and Grit were not mutually exclusive. Warrior's and dark knight's stances were abilities (oGCDs), while paladin's were on the global cooldown. Paladin's and dark knight's stances costed MP to enter.
As DPS Stances were removed completely with the release of Shadowbringers, 
gunbreaker never had a DPS stance. Both of paladin's stances, Shield Oath and Sword Oath, were reworked into traits. Shield Oath was replaced with Iron Will. Tank Mastery was added to all tanks at level 1, making them innately take 20% less damage – the same amount tank stances originally mitigated.
All tanks are now expected to have their tank stance active at all times in 4-player content. Tanks can manage their enmity in 8-player content with Shirk or by simply toggling off their stance if they are encroaching on lead enmity.
Healers
Up until Shadowbringers, all healers had access to Cleric Stance. During A Realm Reborn and Heavensward, it swapped their mind and intelligence attribute, and further increased the damage of offensive spells by 10% while decreasing the potencies of healing spells by 20%. This resulted in the potencies of all healing actions (with the exception of percentage-based healing actions, such as Benediction) were heavily decreased, and the potencies of all offensive actions were greatly increased.
During its Stormblood instance, it was reworked by simply increasing damage dealt by 5% for 15 seconds.