Hi you, can configure vault use in Combat > Demonhunter then the section. If you scroll down the page specific to vault allows
* Always (Any time routine thinks its a good idea)
* In Combat (defined as having a current target)
* Out of Combat (defined as not having a current target)
If its vaulting too much you can increase the "Recast Delay" for vault with a slider in the same settings area.