Fathom-Guard Skarkkis: The tank for this boss must tank both the hunter and his pet. Healers need to focus on both keeping this tanks health up as well as the raids health. Leeching Throw and Multi-Shot abilities affect the raid as well as the tank. A Shadow Bolt from Fathom-Lord Karathress combined with the damage from a Leeching Throw can kill a raid member.
The tank needs to make sure they keep aggro on the hunter pet or it will charge off and start damaging healers and damage dealers in the raid. Once this mob is dead, one healer moves to heal Fathom-Lord Karathress tank and the tanks healer. The other healer moves with the rest of the raid, healing both raid members and the other tanks.
Fathom-Guard Tidalvess: The shamans Spitfire totem does a lot of damage to the raid. It needs to be burned down by raid every time this totem appears. The other totems can be ignored. The shaman also does significant damage to the tank tanking him.