As a werewolf who tries to chase the vampires, the stage 4 ones can disappear into mid run :O I wish my woofer could stealth or cloak lol. Try out Level 4 vampire 😊

I personally love stage 4 over stage 3 for the passive since it makes my DK's stamina efficiency in Cyrodiil fights pretty nice. I end up running a lot, and I will weave in Elusive Mist every so often to keep the momentum going.

As moo_2021 pointed out though it's great for escaping, but not necessarily the actual fighting itself. You can get lucky ambushing someone, but you won't get any kind of sneak attack bonus off it outside the stage 2 passive. The passive also suffers from the fact that any breaking in the running animation has the passive end so liberal use of jumping and auto run is recommended if you wish to stay invisible for any length of time.