Frostmourne Cavern quest bug

[akrasia]

Here is an image attached highlighting my currently plight. In retail, you are supposed to be able to walk right into the cave and activate the orb to begin a cut-scene featuring Arthas. As you can see, the other quest for Vegard has bugged and the area is overwhelmed by high level mobs which I cannot circumvent no matter what I try. https://imgur.com/a/ViwQE

[Swarmer]

get some tank to help you and run to the hammer on the right to click it so the orb spawns and kill the mobs