The vault of glass raid's final boss Aetheon should not be able to be lured off the cliff in the back. I have seen multiple people and been in a hard raid where the people just drop him off the edge. It may take a couple of tries but when we got the pattern right we were able to kill him in less then 10mins.
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It's not a glitch. Anyone can fall off the side. It's a strategy. Everyone plays the game differently.