No, they shouldn't. At least in Oblivion, they were different. They were modififed by a Daedric pact. You may think it is stupid, as well as some other people, but it was balanced. Vampirism is not suppose to be a huge power-up like Lycanthrope was made to be.
I'm wearing a fullsuit of armor by facial features are invisible to you. How do you know I'm a vampire. The Cyrodillic vampires make this big claim about having made a pact with a daedric lord but it flies in the face of established lore. Nine clans in daggerfall grew weaker without feeding and they could all blend into human cities blood or no.
When they made Oblivion they completely forgot about the vampires in daggerfall and only remembered the three clans from Morrowind.
Why is the feeding system stupid? If you want to remain undetected and live in civilization, you feed. If you want to be a powerful recluse, don't feed. Sanguinare Vampiris is a disease, and the vampiric effects are merely symptoms of it and blood is kind of like an antitode or a tylenol. Keeps it at bay.
Because it takes the villianious nature out of vampires. The weaker ones feed on humans while the stronger ones ignore the thirst.....
Please do not try to justify the looks of the other races. There is a distinct appearance of a vampire that seperates it from other races. Their eyes in Oblivion, Skyrim and even Morrowind are unique. Have you seen an Imperial with sulfuric eyes? Or a Breton? Or even a Redguard?
I've seen a Dunmer with purple eyes. Interacial children in Tamerial inherrent the mothers racial traits with some aspects of the father left behind. If one sees a Imperial with sulfuric eyes you could assume they had a human mother and a mer fathert(who can have sulfiric eyes).