What exactly is going wrong?
Eye beams - people need to learn to move out of.
Stone Grip - add this as a debuff to your Grid, having it show who has Stone Grip before they start taking loads of damage makes it much easier. Remember they will die anyway though if dps isnt fast enough on the hand.
Left Arm - we just heal through the left arm damage, its a lot but should be manageable.
Tanks - make sure you have a couple on Kologarn to swap after a couple of debuffs. Have another tank for the adds and tank them out the way somewhere.
Rivers know this: there is no hurry. We shall get there some day.