With 80% spell absorption or 70% magic resistance good luck having any effective offensive with magic. The ABSOLUTE FACT IS. The VL can only defend from physical attacks by running which isn't always an option. Magical defenses are easy to come by even transformed.
What if there is no water, what if we just go behind a tree so you can't target us with your ability without coming back onto land. What if the sun is up nerfing your ability to regenerate. I runaway because my offensive powers are useless due to magic defenses is called retreating.
There's still a chance something would work.
And if the battle has gone on to the point where the sun is up, the smartest thing to do would be to revert back to human form and use the fully realized Dovahkiin powers, but that might be cheating.
If reverting is cheating/impossible... I'd just retreat. No shame in that. Or, I'd use the idiot townsfolk or nearby creatures as meat shields. Strength is not just physical power. [Insert wise proverb here.]
Edit: it should also be remembered that when people become Vampire Lords, they cease to be humans and the Vampire Lord form is their true form.