Sharkkis doesn't hit too hard unless he is under the effect of The Beast Within. An ability that increases not only his attacks but his pets attacks as well. The same tank should also try to pick up his pets. Healers should pump heals during this time. After he is dead, Karathress will gain the ability to use The Beast Within. Most healers should now be focused on Karathress Tank.
Ranged DPS should now be running over to the last add Caribdis. Avoid the Whirlwind ability, though it does not do any damage is greatly increases cast time and lifts you in the air for a few seconds. Her heals should also be interrupted. She also has an ability called Tidal Surge. Its a 10yard AoE that freezes the raider. No one should be close to her other than the tank.
During this time most of the melee should stay with Karathress to focus on the remaining Pet adds and Spitfire Totems. Karathress is NOT to reach below 75% health before ALL adds are dead!
Once Caribdis is killed, Karathress gains her ability Tidal Surge. Everyone may now focus on Karathress. Its game over for him at this point. Make sure to focus Spitfire Totems and have big heals on the tank during The Beast Within and there should be no problems!
Pull and Hold assigned bosses to corresponding positions.
Keep Tidalvess and Sharkkis stacked.
Keep Sharkkis pets in stack
Move Karathress once Tidalvess is dead.
Spitfire Totems MUST DIE. Main Focus.
Melee will stay with Tidalvess and Karathress for totems.
Follow kill order.
Ranged avoid Whirlwind when killing Caribdis.
Big heals when The Beast Within is active.
Don't let anyone die.