Arcane Missiles

Arcane Missiles is a channeled mage spell that shoots a series of missiles at the target dealing direct arcane damage. It has a 40% chance to be triggered by all offensive spells.

Table
Launches three waves of Arcane Missiles at the enemy over X sec, causing Y Arcane damage per wave. Each offensive spell you cast has a 40% chance to Activate Arcane Missiles.

Talent improvements
Arcane Missiles' full potential in PvE is only fully achieved when used by an Arcane Mage under the effect of Missile Barrage. The buff triggered by this talent halves AM's cast time, making it the Arcane Mage's highest DPS spell temporarily.

The Improved Arcane Missiles talent will reduce the chance that damage taken will interrupt channeling. At max rank, Arcane Missiles will never be interrupted by damage.

As with all mage spells capable of critical hits Arcane Potency, Arcane Power, Molten Fury and Shatter can increase the effective damage output of this spell.

Impact from the Fire talent tree now works with Arcane Missiles. Each tick of damage is capable of stunning its target, and with 5 ticks of damage per cast, the proc has a good chance of taking effect on a target who receives all ticks of the spell.

Tips and tactics
Though a powerful spell, Arcane Missiles is often overlooked by many players due to its many weaknesses. Primarily, it is very mana-inefficient and unlike all other mage spells, the full mana cost is used at the beginning of the spell, as opposed to when the spell is actually cast. Thus, if you cancel the spell halfway through or are silenced or counter spelled, you pay for the full cost of the spell, despite the fact that you only output a fraction of the damage. Another large disadvantage of the spell is that it requires you to stay in one space for the 5 second duration, making you a sitting duck in PvP situations (A sitting duck that happens to be shooting magic missiles at foes, anyways) and keeping you from gaining space between you and your enemies.

With the right talents, however, Arcane Missiles can be somewhat useful. With Arcane Subtlety, it also has a very generous damage to threat ratio. A full talent upgrade makes it immune to pushback by regular damage, though abilities like Kick and Shield Bash will still stop the casting. It also receives 142% of your bonus spelldamage (and as high as 188% with Empowered Arcane Missiles).

Arcane Missiles' full potential in PvE is only fully achieved when used by an Arcane Mage under the effect of Missile Barrage. The buff triggered by this talent halves AM's cast time, making it the Arcane Mage's highest DPS spell temporarily.

An often overlooked PvP benefit is the rapid speed with which it hits opponents causes regular spell interruption. Between this and Slow, an Arcane mage can make it exceedingly difficult for an enemy player to get off spells with a cast time.

Another helpful talent is Arcane Concentration. A common tactic in groups when so talented is to cast a fast, cheap spell (like Scorch or an upgraded Frostbolt) until clearcasting is achieved, then cast a free Arcane Missiles.

A notable effect of the fact is that "on spell hit" abilities, such as Mark of Defiance, can proc off each missile, similar to "on spell crit" abilities. However, "on spell cast" abilities, such as Mystical Skyfire Diamond, only have a chance to proc on each casting of the spell, not on each bolt.

This spell can also be useful against rare enemies who are immune/resistant to both Fire and Frost damage. One example of those is the Boiling and Scalding elementals in Thousand Needles, immune to Frost and highly resistant to Fire.

Known bugs

 * There is a bug that prevents base mana regeneration when using the Clearcasting effect for Arcane Missiles.
 * As of patch 4.2.0, there is also a known bug where the tooltip for Arcane Missiles is showing the incorrect proc rate (currently showing 100% instead of 40%).