If the ring was perfectly flat, vampires would have a difficult time. However, as I have said numerous times, werewolves are simply too offensive for a game like Skyrim. Sure, you can make the argument that werewolves are fast enough and do enough damage to one-shot vampire lords, but in a one-on-one battle, it would be impossible to regenerate health. Furthermore, vampiric grip isn't meant to be used for sustained periods. Grip, then shoot. Furthermore, I'm pretty sure it goes right through magic resist. And for general use? Vampire Lord is simply more versatile.
Versatile, sure, but that just means that WW's master their abilities faster. All those moves cost magicka, lots, and some need a cooldown. If that VL cant get through the WW's summons, which would be tough, since they attack what u attack, and would ignore the gargoyles leaving wasted magicka for the VL, then he's done. Stun locked and killed in 5 seconds. Less, if the VL is a mage VL, since theyd have even less health. VL's can absorb magicka, but how far will that take 'em when they'd probably have like 3 or 4 hundred health, and my claws do over a hundred damage WITHOUT criticals? Its quite possible the VL would get 1 or 2 hit, then dead if he's a mage.