First time I ran into some Fangers I found them to be quite tough, but my excuses are it was fairly early on in the game and I'm a noob when it comes to games like Skyrim. The first couple of Novice Vampires weren't a problem, it was the Master Vampire who did me in several times before I got the better of him.
What I have realised about Skyrim Vampires is that they're a bit like the "Twighlight Saga" ones, in that they can walk around in sunlight without catching on fire!!
Spoiler Well, assuming Alva in Morthal is actually a Vampire of course!