Legendary ring, what it actually does and when to use it

3 types of legendary rings

Each ring have certain stats for your class.
Also, when you use the ring, it also differs if you are healer, tank or dps.

Healing Ring
Increase healing and absorption by 25% for 15 sec.
When it ends, each player affected will shoot a AoE shield on friendly players within 20 yards.
The shield absorbs 25% of the healing that was done during the 15 sec  

Dps Ring
Increase dmg by 25% for 15 sec.
When it ends, each player affected will shoot an Aoe Blast within 20 yards.
The dmg of the Blast is 25% of the dmg that was done during the 15 sec  

Tanking ring
Increase Versatility by 50% for 15 sec.
During these 15 seconds, all dmg and healing is divided among allies instead of just 1 or some players.

Each type of ring shares a 2 min CD with the same type of ring.

When you should use each ring for each boss encounter in Hellfire Citadel

Hellfire Citadel

Dps Ring
Use when first Siege Vehicle arrives
When CD is ready use it when another Siege Arrives
If players struggle with Martak in the beginning, use the ring at start instead.

Healing Ring
Use when there are more than one Felcaster that shoots Fire Volleys after they transform at 50%

Tanking Ring
If you have high stacks of Slam from the Big adds Gorebound Berserkers.

Iron Reaver

Dps Ring
Use in the beginning of the fight before there are loads of mechanics to avoid.

Healing Ring

Use when Boss does his Second Pounding
When CD ready, use on following Pounding

Tanking Ring
Use when boss does Artillery on you.

Kormrok

Dps Ring
Use when Grasping Hands Drags the players to the pool.

Healing Ring
Use when grasping hands and Pound happens at the same time
Or use when Grasping hands and Explosive Burst (on tank) are at the same time and tank is stuck on raid.

Tanking Ring
Use on Swat (the knockback) then it helps the raid at the same time when all 3 waves are coming at them.

Hellfire High Council

Dps Ring
Use when Gurtogg is at 30%
Use when Blademaster is at 30%
Use when Dia is at 30%

Healing Ring

Use when the room turns dark and shadow adds fly across the room (Wailing Horror, Darkness)

Tanking Ring
Use when getting to high dmg from Gurtogg as an extra defensive ability
Use when Wailing Horror, Darkness if melee fails at moving from shadow adds.

Kilrogg Deadeye

Dps Ring
Use when first players runs in the vision thelp the players outside handling the adds with less dpsers
When CD ready, use when a group comes out of the vision

Healing Ring
Always use when boss does raid dmg, Death Throes.

Tanking Ring
The tanking ring is a backup on this fight.
Use if there are more than one Hulking Terror
Use if a Hulking Terror has not been interrupted

Gorefiend

Dps Ring
Use directly at start
Use at every Feast of Souls

Healing Ring
Use at every Feast of Souls

Tanking Ring
Use as an extra mitigation when tanking the Gorebound Spirit
Use if a Gorebound Spirit has not been interrupted.

Shadow Lord Iskar

Dps Ring
Always use when adds come

Healing Ring
This ring will be used as backup when raid takes unnecessary dmg from Chakram, Fel Incarnation

Tanking Ring
Use when tanking the adds

Socrethar The Eternal

Dps Ring
Use when first Dominator comes out from portal (BL on second Dominator)
If it takes more than 2 min to get into phase 2 and the first Dominator, use the Dps ring at start as well.

Healing Ring
In phase 1: Use at Reverberating Blow
In phase 2: Use when boss does Apocalypse

Tanking Ring
In phase 1: Use at 3rd Reverberating Blow
In Phase 2: Use when Dominator is out

Fel Lord Zakuun

Dps Ring
Use at pull
Use when boss is at 30%

Healing Ring
At Phase 2: When entire Raid takes loads of dmg
If possible, use also when boss is under 30%

Tanking Ring
On Phase 2: When boss is disarmed
Use when boss is under 30%

Xhul´horac

Dps Ring
Use when first Big add is out (Vanguard)
Use when second Big add is out (Omnus)
Use when boss is Overwhelmed in the end

Healing Ring
Use when first Big add is out (Vanguard)
Use when second Big add is out (Omnus)
Use when boss is Overwhelmed in the end

Tanking Ring
Use when tanking first Big add is out (Vanguard)
Use when tanking second Big add is out (Omnus)
Use when boss is Overwhelmed in the end

Tyrant Velhari

Dps Ring
At pull: Use and burn boss down so first add comes and pass the phase faster
Phase 2: When 2nd add comes. Use it togehter with Timewarp
Phase 3: When 3rd add comes, together with the 20% increase dmg debuff it will be awesome

Healing Ring
Phase 1: Use as backup only if raid takes to much dmg from Edict Condemnation or Touch of Harm or if melee stand close on Infernal Tempest. But have the cooldown ready when phase 2 comes (boss 70% HP)
Phase 2: Raid will take loads of dmg from Corruption. Use after BL.
Phase 3: Raid will take 10% extra dmg the entire phase and may take dmg from the Bulwark and its pools. Use when needed.

Tanking Ring
Phase 1: If melee stands to close on Infernal Tempest.
Phase 2: When add comes, Raid will take loads of dmg from Corruption.
Phase 3: Raid will take 10% extra dmg the entire phase and may take dmg from the Bulwark and its pools. Use when needed.

Mannoroth

Dps Ring
Use when first Doom Lord is out
When CD ready, use when adds are spawned

Healing Ring
Use when raid takes too much dmg from adds at start
At phase 4: When Mannoroth´s abilities are empowered (Empowered Mannoroth´s Gaze)

Tanking Ring
Use as extra mitigation on Glaive Combo

Archimonde

Dps Ring
Phase 1: When Deathcaller add is spawned
Phase 2: When Deathcaller add is spawned
Phase 3: When inside the Nether or when outside the Nether when Infernal adds are spawned

Healing Ring
Phase 1: When boss throws up a player (Shadowfel Burst)
Phase 2: When players run out from raid at Shackled Torment
Phase 3: When raid takes heavy dmg from Infernal adds and Rain of Chaos

Tanking Ring
Phase 1: When Deahcaller add is out (Death Brand)
Phase 2: When Deahcaller add is out (Death Brand)
Phase 3: As an extra mitigation, since you get dmg from many directions (Boss, adds, Rain of Chaos)