The option to become a vampire has been a part of the Elder Scrolls games since Daggerfall, but Skyrim's Dawnguard expansion was focused on the sun-dodgers—letting you become either a shapeshifting Vampire Lord, or a crossbow-wielding vampire hunter. What you may not realize is that add-on also defanged vampires to a degree.
Dawnguard reduced the damage caused by a couple of varieties of vampires, disabled a perk that let boss-level vamps ignore a percentage of armor while wielding maces, and changed the frost resistance and fire weakness stats of all vampires. What's more, the effect of hitting stage four of vampirism, where you're supposed to be "hated and feared," was reduced. NPCs will no longer attack a stage four vampire on sight—only one who is in their Vampire Lord form, or feeding.
