Kologarn

Overview
Kologarn and his two Arms can all be targeted, so the raid can choose what, when and how to kill.

Kologarn himself has the most hit points and number of abilities. His Overhead Smashes require an Offtank, as they reduce the armor of the main tank by a big percent, and stack. Focused Eyebeams will need to be avoided by everybody (similarly to the Tribunal of Ages event in Halls of Stone). If there are no players in melee range, Kologarn will quickly wipe the raid with Petrifying Breath. If both of his Arms are dead, he will channel Stone Shout, which is massive raid-wise AoE your group will want to avoid.

Kologarn's Right Arm has only one ability, and it is Stone Grip. It grabs 1-3 players and inflicts damage to them, until the Arm is damaged enough to drop them, or until at least one of the players dies. Killing the Arm reduces Kologarn's health by 15% until the Arm respawns, which takes ~15-30 seconds; it also spawns 4 Rubble creatures, that have AoE and should be offtanked.

Kologarn's Left Arm casts Shockwave periodically, which is a raid-wide AoE the healers will just need to heal through. Killing this Arm also decreases Kologarn's health by 15% for ~15-30 seconds until the Arm respawns, and causes 4 Rubble creatures to appear.

Tactics (10-man version)
1. MT1 runs in and starts tanking on Kologarn (the body).
2. The healers position themselves in a triangle behind the MT, maintaining 5-10 yards distance (Don't stand too close to the body or you will get spell interrupted).
Ranged DPS take positions behind and to the sides of them. (this will leave space in the back for everyone hit by the eye beam to run around).
Melee DPS stand close to the tank, you can hit the Right Arm from there and never have to move the whole fight.
3. All DPS start nuking the "Right Arm" on the left side, going all out. Use all cooldowns, trinkets, buffs, bloodlust/heroism if available.
4. Before the arm dies, MT1 and MT2 switch tanking on The Body. (this is to get rid of the debuff)
5. MT2 is now on the boss, so MT1 picks up the adds who spawn when the Right Arm dies.
6. Melee DPS continues on The Body. Ranged AoE DPS nukes the adds, then proceeds on The Body.
7. MT2 and MT1 switch tanking on The Body again, as soon as the debuff on MT1 is gone again.
8. As soon as the Right Arm respawns, all DPS have to switch to it immediately.
9. Keep doing this until Kologarn is down.

Notes:
- The tank on the adds can't use abilities like Challenging Shout. This will cause aggro from The Body, and cause the issue with the 1st in aggro list not being within melee range of The Body - Petrifying Breath will kill the tank.
- Tank switches need to be done everytime the crunch armor debuff has run out on the spare tank.
- Just ignore the Left Arm. The AoE damage done by it is healable, and if you kill it you get into more trouble by having to kill additional adds. Which means losing DPS on The Body/Right Arm. If you have a hunter or a shaman, use their nature resistance buffs to reduce the AoE damage.