Interrupts in Mythic+

Special thanks to the /r/wownoob community for providing feedback on my original post.

The term "interrupt" can sometimes mean different things in World of Warcraft.

In this post, I'll categorise "interrupts" as either interrupts or crowd control - often, when the term "interrupt" is used in-game, the player is referring to the former; but, sometimes, the player is referring to the latter — there are subtle differences between the two, but both can be used to stop an enemy's cast or channel.

It is important to understand the difference between the types of abilities that can stop a cast or channel when running Mythic+. It is equally important to understand which ability is your interrupt, and all of the crowd control abilities available to your class or spec. 

If you are asked to "interrupt" something, you will want to know which of the two you are being asked to do. A good rule of thumb is, use your interrupt if it is appropriate; otherwise, crowd control is being asked for. 

Interrupt

An interrupt ability can be used on any enemy if the cast-bar is yellow (or, in the case of a channelling spell, green). It will not work on casts if the cast-bar is grey. In addition, an interrupt will also prevent the target from casting again for a duration of time.

Each spec has either zero or one, or two interrupt abilities - most specs have one.

Melee DPS typically have a shorter cooldown on their interrupt ability; Ranged DPS typically have a longer cooldown on their interrupt ability; Healers typically do not have an interrupt ability.

Advantages

• Can be used against any enemy
• Prevents the enemy from casting again for a duration of time
• This can force a caster enemy to run into melee range of the tank
• Are not on the global cooldown

Disadvantages

• Cannot be used on casts where the cast-bar is coloured grey
• These will only work against a single target - however, Solar Beam also applies an AoE silence at the target's location.

List of interrupt abilities by class

Mouseover the ability to see:

• its cooldown,
• the amount of time it prevents the enemy from casting again, and
• its range

Noteworthy abilities include Solar Beam which also AoE silences, Wind Shear which is the interrupt with the shortest cooldown in the game (and is the only interrupt available to a healing spec), and Spell Lock/Axe Toss which is actually a demon's ability, not the player's.

• Warrior - Pummel
• Paladin - Rebuke (Protection also has Avenger's Shield, but this only interrupts the target)
• Hunter - Counter Shot (Marksmanship/Beast Mastery) or Muzzle (Survival)
• Rogue - Kick
• Priest - Silence
• Shaman - Wind Shear
• Mage - Counterspell
• Warlock - Spell Lock (Felhunter) or Axe Toss (Demonology's Felguard)
• Monk - Spear Hand Strike
• Druid - Skull Bash (Feral/Guardian) or Solar Beam (Balance)
• Demon Hunter - Disrupt
• Death Knight - Mind Freeze and Shambling Rush (Unholy's Ghoul)

Crowd Control

Crowd control abilities can cause the enemy to "lose control", with the side-effect being that their cast or channel will be stopped - these abilities are frequently used in Mythic+ with the intent to stop a cast or channel. They cannot be used on enemies that are Immune to the effect. Usually, enemies that are larger in size or more difficult are immune to crowd control. These abilities do not prevent the target from casting again for a duration of time. 

These abilities are sometimes referred to as an interrupt because using them can stop the cast of an enemy - however, unlike an interrupt, the ability is not specifically designed to stop casts. These are designed, for example, to Stun the enemy - the fact that the cast was "interrupted" was a byproduct of the Stun.

Crowd control abilities include:

• Stun (such as Maim, Shadowfury, Hammer of Justice, or Intimidation)
• Incapacitate (such as Freezing Trap or Imprison)
• Disorient 
• Silence
• Displacement/Forced Movement (such as Shining Force or Typhoon)
• Root (has been included for completeness - but roots will not stop a cast or channel)

These categories were defined by /u/cyanraider, who has provided more detailed information here.

Advantages

• Can be used if the cast-bar is grey
• These abilities are sometimes AoE (such as Chaos Nova, Leg Sweep, and Incapacitating Roar)

Disadvantages

• Some monsters are immune to these effects
• There is no universal rule, or clear way to know, whether or not a particular monster is immune to these effects. Typically, monsters that are larger in size or more difficult than most are likely to be immune.
• Will not prevent the enemy from casting again immediately after
• However, often the monster's ability goes on cooldown and this will prevent the monster from casting again immediately. This varies depending on the monster and the ability.
• Are on the global cooldown

Example

Amarth is a dungeon boss - so crowd control will not work because he is immune. However, the cast bar for Necrotic Bolt is yellow, so an interrupt will work.

The Reanimated Crossbowman is casting shoot, but the cast bar is grey. An interrupt will not stop this cast. He is a small monster who is not difficult - so he will not be immune to crowd control. Stuns, fears, and all other crowd control will work on the Reanimated Crossbowman to stop his Shoot cast.

The Renimated Mage is casting Frosbolt Volley. The cast bar is yellow and he is a smaller monster. Both an interrupt and crowd control will work! An interrupt will also prevent him from casting Frostbolt Volley again for a duration of time.