Howdy, I think that greater wheel of pain having 300k HP and Vault, massive reinforced steel object, having 150k Hp is not the greatest of decisions. In my opinion vault should have at least 800K-1KK of HP :).
The vault had 600k before. People used it as landclaim. Enough said.
So they are using greater wheels now? xD
Stone thrones have 300k HP and are cheaper