Arcane Barrage is a level 10 Arcane mage ability designed to consume Arcane Charges. Beginning at level 34, Arcane Barrage also strikes additional nearby enemy targets equal to how many charges were consumed.
Added in Patch 3.0.2 as the 51-point talent for Arcane, Arcane Barrage was designed as a single-target instant cast spell with an unusually high spell power co-efficient. Arcane Barrage's intention was to be used alongside [Arcane Blast] in order to consume its debuff and allow the Mage a way to conserve mana without interrupting casting (much like the spell does currently with Arcane Charges). However, any other Arcane damaging spell was capable of consuming Arcane Blast's debuff, and often [Arcane Missiles] was used instead as it had superior damage and no mana cost. This led to the spell being seldom used in PvE prior to its redesign in Patch 5.0.4.
Patches and hotfixes
Patch 8.0.1 (2018-07-17): Damage done per Arcane Charge reduced to 30% (down from 60%). Mana cost removed. Cooldown decreased to 3 seconds.
Patch 7.1.5 (2017-01-10): Damage increased by 12%.
Patch 7.1.0 (2016-10-25): The cleave effect of this spell has been split into a second rank, available at level 34.
Patch 7.0.3 (2016-07-19): Damage increased by 74%, damage increase per Arcane Charge increased to 60% (up from 50%). Cooldown increased to 4.5 seconds (up from 3 seconds).
Hotfix (2014-12-08):Damage has been increased by 16%.
Hotfix (2014-10-14):Resolved a script error with Arcane Barrage
Patch 5.2.0 (2013-03-05): Damage has been reduced by 16.1%.
Hotfix (2012-09-20):Arcane Barrage damage has been reduced by approximately 3.5%.
Patch 5.0.4 (2012-08-28): Now affected by the Arcane Charge resource mechanic, and may now cleave nearby targets based on charges. Mana cost reduced to 0.5% base mana (down from 11%). Cooldown reduced to 3 seconds (down from 4 seconds).
Patch 4.1.0 (2011-04-26): Damage has been increased by 13%.
Patch 4.0.6 (2011-02-08): Mana cost has been reduced by 8%.
Hotfix (2011-01-18):The mana costs of the following mage spells have been reduced, but they still require the previous percentage of base mana in order to be cast: Arcane Barrage (11% of base mana), [Arcane Blast] (7% of base mana), and [Fireball] (12% of base mana). As an example, Fireball requires 16% base mana to cast, but only consumes 12% of base mana.
Patch 4.0.3a (2010-11-23): Damage has been increased by 5% and its cooldown is now 4 seconds, down from 5 seconds.
Patch 4.0.1 (2010-10-12): Changed from being a talented spell to a specialized spell, obtained by all mages choosing Arcane. Replaced by [Arcane Power] as final talent in the Arcane tree.
Patch 3.0.9 (2009-02-10): Spell power co-efficient reduced to 71.43% (down from 85.71%).
[Arcane Pressure], 
[Chrono Shift], 
[Resonance]
[Arcane Blast] in order to consume its debuff and allow the Mage a way to conserve mana without interrupting casting (much like the spell does currently with Arcane Charges). However, any other Arcane damaging spell was capable of consuming Arcane Blast's debuff, and often 
[Arcane Missiles] was used instead as it had superior damage and no mana cost. This led to the spell being seldom used in PvE prior to its redesign in Patch 5.0.4.
Patch 8.0.1 (2018-07-17): Damage done per Arcane Charge reduced to 30% (down from 60%). Mana cost removed. Cooldown decreased to 3 seconds. 
