Patch 8.0.1(2018-07-17): Evocation once again increases mana regeneration for its duration rather than restoring a fixed amount of mana.
Patch 7.1.0(2016-10-25): Now available at level 20. Cooldown increased to 3 minutes. New rank available at level 56 that reduces its cooldown to 1.5 minutes.
Patch 7.0.3(2016-07-19): Evocation no longer consumes Arcane Charges, and now restores 100% of total mana over 6 seconds. Cooldown reduced to 1.5 minutes. New spell animation.
Patch 6.0.2(2014-10-14): Now available only to Arcane mages.
Patch 5.2.0(2013-03-05): For Arcane Mages, Evocation now restores 40% (was 60%) of total mana over 6 seconds, and consumes all Arcane Charges. For each Arcane Charge consumed, the total amount of mana regenerated is increased by 10%, up to a maximum of 80% over 6 seconds. Evocation remains the same for Fire and Frost.
Patch 5.0.4(2012-08-28): Now available at level 40. Cooldown reduced to 2 minutes. Now causes the caster to gain 15% of total mana instantly and 45% of total mana over 6 sec.
Abilities that grant a power increases (such as Evocation) were changed to guarantee a consistent number of ticks of regeneration at the increased level. For Evocation, this means that as soon as the spell is cast, a single tick of mana regeneration will be awarded at the normal level, then exactly 2 seconds and every 2 seconds after, the 1500% of mana regeneration will be returned, guaranteeing a full 4 ticks of increased regen every time. Previously, with unfortunate timing, increased mana would be returned on only 3 ticks.
Animation changed to the new cyclone spell effect. Undocumented.