Now that I have finished the Dawnguard MQ, however, I am not seeing any Vamp attacks and I miss them. Not only do I miss the Vamp attacks, I actually miss the threat they pose to the citizenry. I want to be a hero that saves the day!

So I see both sides of the argument. Nevertheless, I think there is a middle ground that can satisfy both sides: let the player decide if an NPC is essential or not.
My suggestion would be that all service-provider/quest-related NPC's be marked as essential initially. The player would then have the option to mark them as non-essential through the selection of a dialogue option. The option might be something like "Are you worried those vampires might strike here next?" By selecting this option, the player would change the NPC's status from essential to non-essential. With this option, those that want their NPC's to stick around would be satisfied, while those that want the ambiance provided by the danger of vamp attacks could also have their game operate the way they want.
I say give the player the choice.