Ahk'Mun Rhoen possess a strong knock back effect and a long duration stun. It is highly recommended that you not fight him on the tower where he spawns. Choose one person to climb the tower and aggro Ahk'Mun Rhoen. Then pull him down and have your tank put their back against something to keep Ahk'Mun Rhoen from wandering around while you fight. It is entirely possible to wipe due too the long duration stun if the knock back is not controlled. Other than that it is a fairly straight forward fight. Keep healers unstunned, keep slow on the epic monster and, and keep tanks back to the wall.