Damage over Time

Damage over Time, generally abbreviated as DoT or simply dot, refers to inflicting some damage on one's foe which will be applied at a regular interval for a limited duration. Abilities and debuffs that inflict damage over time are referred to as DoTs. Some AoE effects also deal damage over time.

Typically in World of Warcraft, the damage from DoTs is applied every X seconds, in ticks. Every X seconds the DoT will 'tick', dealing damage. Ticks usually deal a regular amount of damage, but in some cases (such as Agony) this amount increases, with later ticks dealing more. Each DoT has a base number of ticks, and a base tick frequency (often once every 3 seconds), which multiply to equal the total duration of the effect. Haste can increase the speed of ticks, causing damage to be dealt more quickly, and if sufficient, will result in extra ticks being added to the effect, roughly maintaining the overall duration of the DoT but greatly increasing both its total damage (and therefore cost efficiency) and the speed at which it deals damage.

DoTs may be applied using a variety of methods — from a spell, a trap, a weapon, a poison, or some other form. Most DoTs are target specific, but some are also used as Area of Effect (AoE) attacks.

While all damage dealing classes have some form of DoT, the Affliction Warlock and Shadow Priest are the most reliant on DoTs as the backbone of their DPS rotation.

Discussion
Damage over Time effects are most effective when they are allowed to run their full course. Also, DPS based on multiple DoTs has a significant ramp-up time as it takes several Global Cooldowns to apply them all to a target. As such, DoTs provide sustained DPS, without the "burst damage" of an equivalent Direct Damage attack.

DoTs in PvE are most effective in extended fights against one or more long-lived targets, and least effective in short trash pulls where the targets are downed quickly, or fights that require frequent switching to new targets. Specs relying on DoTs often lack burst capabilities, or may have to use an alternate rotation (often not involving DoTs) when burst damage is required. DoT-reliant specs must decide early on whether DoTs will be required for dealing with any given target; applying them to a target that is quickly downed is a waste of mana and potential damage output, while failing to apply them to a target that takes a more significant time to defeat will usually result in similar waste of mana and damage output, due to the substitution of less desirable damage-dealing abilities. DoT-reliant Warlocks and Priests can find it hard to maintain competitive DPS against trash without high-end gear, and will often fall back solely on Area of Effect spells in those situations.

One significant advantage of most DoTs is the ability to apply them to an unlimited number of targets. This allows these specs to deal huge amounts of damage on multiple targets, albeit relatively slowly and in a manner that is often easy for healers to respond to with multiple-target heals. In PvE, on so-called "council fights", where two or more boss targets share a health pool, this effect can significantly amplify DoT class DPS. This technique is referred to as "multidotting".

In PvP, DoTs are vulnerable to being dispelled, but have the advantage of continuing to cause damage if the caster is silenced, out of range or even dead. This leads to tactics such as the warlock's infamous "dot, dot, dot, fear". The target has no chance to dispel the DoTs until they have broken the fear, while the caster is free to heal, run away or cast further offensive spells while their opponent takes damage from the DoTs. To compensate for their vulnerability to being removed before they have fully affected a target, some DoTs will also cause additional damage or other effects if dispelled. For example, the Affliction warlock DoT Unstable Affliction will damage and silence the dispeller for 4 seconds.

One limitation of DoTs is their ability to break crowd control effects, such as Polymorph. Some crowd control spells can be modified - such as with Glyph of Polymorph - to remove all DoTs from the target, preventing this conflict.

As of patch 4.0.1, all DoTs can crit, and all spell DoTs and some physical DoTs innately scale with haste. Unlike prior implementations of DoT haste scaling, DoTs do not lose duration when affected by haste. This functionality was further updated in patch 6.0.1. Between patches 4.0.1 and 6.0.1, the DoT's duration would be the sum of the number of DoT ticks that leaves the final duration closest to the original duration as possible, meaning the duration would fluctuate around the original duration by up to half the tick interval as haste values changed. In 6.0.1, all DoTs retain their normal duration regardless of haste levels. The game engine will fit in as many full ticks as possible within that duration, and then finish the dot with a partial tick representing the portion of a normal tick proportional to ratio of the remainder time to the normal tick interval. For example, a 15 second DoT that normally ticks every 3 seconds ticks 5 times. With 25% haste, it will have a tick interval of 2.4 seconds. It will thus tick 6 times during the 15 seconds, over 14.4 seconds. At the end of the 15 second duration, a 7th partial tick will occur for (0.6 / 2.4) = 25% of a normal tick, resulting in an effective damage equal to 6.25 tick (5 * 1.25), representing the 25% damage increase per time interval from haste. As a result of this change, DoTs no longer have any haste breakpoints and now have a continuous increase in both their damage per second and damage per cast.

Also as of patch 4.0.1, DoTs no longer can be 'clipped'. Previously, if a DoT was refreshed before it had expired, the tick timer was reset, causing a delay of up to double the normal time between ticks between the last tick that occurred and the first tick of the refreshed DoT. Now, the tick timer is constant. If a DoT is refreshed before it expires, the duration of the DoT will be extended by up to the full normal duration of the DoT, and ticks will continue to occur at the prior interval. Between patches 4.0.1 and 6.0.1, this functionality only allowed DoTs to be "clipped" by a single tick before duration was wasted, requiring DoTs to be refreshed between the second-to-last and the last tick to maintain uninterrupted DoT ticks while optimizing duration gain. Patch 6.0.1 extended this period to 30% of the DoT's normal duration. For example, a 15 second DoT can be extended when it has less than 4.5 seconds remaining at no duration loss (the full normal duration is added to the remaining duration). This also applies to many short-duration buffs like Slice and Dice.

Examples

 * Death Knights with Icy Touch, Plague Strike, and Unholy Blight.
 * Druids with Moonfire (in generic caster or Moonkin form), Rip, Rake and Pounce (in Cat Form), and Lacerate (in Bear Form).
 * Hunters with Serpent Sting, Explosive Shot, and Explosive Trap as Area of Effect DoT.
 * Mages with Living Bomb, and Fireball, Frostfire Bolt, or Pyroblast (although these are primarily DD spells, they also add a small DoT even when offspec), If specced, fire spells criticals will put on the enemy a dot through Ignite talent which deals 8-40% of the damage done for 4 seconds.
 * Paladins using Seal of Truth and Consecration in a way. If specced, Divine Storm and Judgement spells criticals will put on the enemy a dot through Righteous Vengeance talent which deals 40% of the damage done for 8 seconds.
 * Priests with Shadow Word: Pain, Vampiric Touch, and Devouring Plague.
 * Rogues with Deadly Poison, Garrote, or Rupture.
 * Shamans with Flame Shock (a DD spell with DoT). Magma, and Searing Totems may also be considered DoT (or AoE).
 * Warlocks with Immolate, Corruption, Agony, Doom, Seed of Corruption, or Unstable Affliction.
 * Warriors with Rend, also if specced, their melee criticals will apply a Deep Wound that deals 60% of weapon damage.

Limitations

 * Most spell-based or poison-based DoTs can be cured by potions or dispelled.
 * Most methods of Crowd Control are broken by damage dealt by DoTs.

Tips

 * Rogues and Cat Form Druids who stealth while a DoT is still on them will come out of stealth when the next tick of damage is inflicted. Vanish will briefly prevent DoTs from pulling a rogue out of stealth.
 * First Aid and Fishing will be interrupted by a DoT.