One of the issue and question have with current systems in 12.1 is that currently the Great Vault doesn’t remove loot from the bonus rolls loot table. Which means that your vault even if it drops your bis might not be the best choice. This is a bit confusing and might penalize players unaware of how the bonus rolls work. So I would suggest to make the Great Vault loot count as if it was bonus rolled in term of bad luck protection when you pick it.