Fae Guardians

Here is a list of all Fae Guardians affected cooldowns:
Death Knight
Blood - [spell=55233]
Frost - [spell=47568]
Unholy - Apocalypse
Warrior
Protection - [spell=107574]
Arms - [spell=227847] / [spell=152277] (Talent)
Fury - [spell=1719]
Demon Hunter
Vengeance - Metamorphosis
Havoc - Metamorphosis
Paladin
All - Avenging Wrath
Holy - [spell=216331] (Talent)
Retribution - [spell=231895] (Talent)
Druid
Restoration - [spell=740]
Guardian - [spell=50334] / [spell=102558] (Talent)
Feral - [spell=106951] / [spell=102543] (Talent)
Balance - [spell=194223] / [spell=102560] (Talent)
Priest
Discipline - [spell=47536] / [spell=109964] (Talent)
Holy - [spell=64843]
Shadow - [spell=228260]
Rogue
Outlaw - [spell=13750]
Assassination - [spell=79140]
Subtlety - [spell=121471]
Hunter
Survival - [spell=266779]
Beast Master - [spell=193530]
Marksmanship - [spell=288613]
Shaman
Enhancement - [spell=51533]
Restoration - [spell=108280]
Elemental - [spell=198067] / [spell=192249] (Talent)
Mage
Arcane - [spell=12042]
Frost - [spell=12472] / [spell=198144] (PvP Talent)
Fire - [spell=190319]
Warlock
Destruction - [spell=1122]
Affliction - [spell=205180]
Demonology - [spell=265187]
Monk
Brewmaster - [spell=120954]
Windwalker - [spell=137639] / [spell=152173] (Talent)
Mistweaver - [spell=115310]

TLDR: Whenever you cast this ability you can:

-Get about 300 mastery and 12% maximum health for 30s (With Niya as your active Souldbind, through 12 stacks of [spell=322721]).
-Reduce someone's damage taken by 10% for 20s with [spell=327694].
-Reduce 20s off the remaining cooldown on the person's Major ability you cast [spell=327710] on while that ability is on cooldown.
-Recover 3 insanity as Shadow or 250 mana as Holy or Disc per direct damage spell cast on the enemy with [spell=342132].

While I wouldn't consider it a super strong option for Disc or Shadow, and while it will be underrated because it doesn't directly do damage. The combination of all the bonuses, low CD and high uptime buffs makes it really powerful and fun as a Holy Priest, and the offensive value, when managing [spell=327710] correctly, can be on par or stronger than the other covenant abilities, specially on M+.

Something I noticed and tested that isn't obvious on the tooltip:

-You CAN cast the spell directly into a target. If the target is an ally, you'll send both [spell=327694] and [spell=327710] to it. If your target is hostile you'll send [spell=342132] into them and get both [spell=327694] and [spell=327710] on yourself.

This means you can save yourself from casting Flash Heal/[spell=186263] in case you want to have [spell=327710] on the ally you cast Fae Guardians on.

Tip: For optimal use I suggest casting it directly on the ally that you want to have [spell=327710] on, then cast Power Word: Shield on the active tank to redirect [spell=327694] to it. After that you can simply focus on dpsing to recover mana through [spell=342132] or just enjoy [spell=322721]'s large mastery bonus (which lasts 10s more than the Guardians).

-Mouseover macro to directly cast it on an ally:
/target [@mouseover,help,nodead,exists]
/cast [help,nodead,exists] Fae Guardians(Night Fae)
/targetlasttarget [@mouseover,help,nodead,exists]

NOTE: Regular mouseover macros don't seem to work atm with the spell.

The Benevolent Faerie buff affects one major CD per spec.

Shadow: Void Eruption
Disc: Rapture
Holy: Divine Hymn

While the Benevolent Faerie buff is active, the ability's CD will decay twice as fast. The buff will automatically target you when Fae Guardians is cast - you have to actively move the buff to someone else if that's your goal. If you don't move the buff off yourself, then Benevolent Faerie is basically a 20 s CD reduction to the CDs listed above. You should probably never use Fae Guardians unless one of these abilities is already on CD.

Some CD mods (such as OmniCC) may incorrectly report how this ability affects your CDs. Refer to the ability tooltip if you want to confirm it's working appropriately, or time the CD with a stopwatch. The ability is currently functioning correctly.