Flash Heal is a level 3 priest's fast single-target healing spell. It sacrifices mana efficiency in order to land a heal faster on someone who might not live to receive a spell with a longer cast time.
Flash Heal excels in situations where speed, not mana efficiency, is the prime concern. Conversely, due to its poor mana efficiency, it is best used only in these situations. Wherever possible, more efficient options such as [Heal] are preferable.
Spamming Flash Heal makes for extremely potent healing, but drains mana at an alarming rate.
The spell has a higher single target throughput than [Binding Heal], but if you are hurt, it is generally a good idea to use Binding Heal instead of Flash Heal.
Patch 7.1.0 (2016-10-25): Now learned at level 5 (was 10) and available to all specializations, but Discipline and Shadow eventually replace it with [Shadow Mend].
Patch 7.0.3 (2016-07-19): Now learned at level 10 (was 7), and is only available to Holy.
Hotfix (2013-09-24):Flash Heal now should correctly receive an increased critical chance from Inner Focus while Surge of Light is active.
Patch 5.2.0 (2013-03-05): Amount of healing done reduced by 20%. However, the re-introduction of [Spiritual Healing] means that for Discipline and Holy priests, there is no decrease to the amount of healing done.
Hotfix (2012-10-01):Flash Heal will now consume both Surge of Light and Inner Focus when both buffs are active.
Patch 5.0.4 (2012-08-28): Now learned at level 7 (was 3).
Hotfix (2011-01-06):Casting Flash Heal while under the effects of both [Surge of Light] and [Inner Focus] will now only consume Surge of Light.
Patch 4.0.6 (2011-02-08): Effects are now consistent with the tooltip.
Patch 4.0.3a (2010-11-23): Throughput increased by another 20%
Patch 4.0.1 (2010-10-12): Now learned at level 3 (was 20). Now costs 28% of base mana, up from 18%, and throughput massively increased.
Patch 0.7 (2004-06-15): Mana cost and heal amount reduced.