I was in the 6-man party version of the dungeon instead of the solo quest version. The NPC on the ground outside the dungeon did not have a yellow quest marker on him so I did not speak to him and went straight through the portal. When I saw the NPC Poharan inside I assumed I was in the quest dungeon. This time I spoke to the NPC on the ground and clicked ' yes ' to enter the dungeon. The solo dungeon is quite different, as you enter straight into the room where Rahmion is. He has 211k HP instead of 3.7kk HP, Poharan does not get stuck to the ground and no other mobs appear. So I was able to complete it no problem.
Thanks for your help.