Heroic Kin'garoth

Tank

• In Phase One:
• Use active mitigation and be 5 yards away from any other player for the Forging Strike hit.
• Taunt off one another once your Forging Strike debuff drops, usually around 2 stacks.
• The off tank should stand on the other side of the boss and soak Diabolic Bombs when the raid is healthy enough to survive the damage.
• Move out of the way of the Ruiner beam as the boss rotates.
• In Phase Two:
• Help damage the add that you have been assigned to.
• Avoid standing in Apocalypse Blast zones.
• Leave the rooms the Fel Reaver adds spawn in before the phase ends to avoid being instantly killed!
• When adds are active:
• When the remaining add activates, tank it next to the boss whilst the other tank re-engages Kin'garoth directly.
• Help spread the damage from a single Demolish debuff.
• Move away from the Decimation zones.
• Stand in any nearby Annihilation zones. Only one player is needed to soak each zone.

Healer

• In Phase One:
• The tank will take heavy damage when taking the second Forging Strike hit in a row.
• Spread 5 yards and do not stand in any Detonation Charges when Reverberating Strike is cast.
• Stand on one side of the boss with the raid, whilst the off tank soaks Diabolic Bombs on the other side of the boss.
• Avoid getting hit by the Diabolic Bombs!
• Ensure the raid is healthy before a Diabolic Bomb is soaked.
• Move out of the way of the Ruiner beam as the boss rotates.
• In Phase Two:
• Have the healers spread between the two groups to ensure that all players receive healing to combat the damage from Flames of the Forge.
• Avoid standing in Apocalypse Blast zones.
• Leave the rooms the Fel Reaver adds spawn in before the phase ends to avoid being instantly killed!
• When adds are active:
• Help spread the damage from a single Demolish debuff.
• Move away from the Decimation zones.
• Stand in any nearby Annihilation zones. Only one player is needed to soak each zone.

Damage

• In Phase One:
• Spread 5 yards and do not stand in any Detonation Charges when Reverberating Strike is cast.
• Stand on one side of the boss with the raid, whilst the off tank soaks Diabolic Bombs on the other side of the boss.
• Avoid getting hit by the Diabolic Bombs!
• Move out of the way of the Ruiner beam as the boss rotates.
• In Phase Two:
• Have the DPS split in half, with each half attacking the add the raid has chosen to kill first.
• Once the add is dead, regroup and start killing off the remaining add.
• Avoid standing in Apocalypse Blast zones.
• Don't bother attacking the boss as he is taking 99% less damage during phase two.
• Leave the rooms the Fel Reaver adds spawn in before the phase ends to avoid being instantly killed!
• When adds are active:
• Focus on killing the Fel Reaver add over the boss.
• Help spread the damage from a single Demolish debuff.
• Move away from the Decimation zones.
• Soak Annihilation zones that spawn in the encounter area. Only one player is needed to soak each zone.

Source: Kin'garoth Antorus Raid Strategy Guide - Guides - Wowhead