From what I heard its an intended feature thats meant to make the Volkihar look more monsterous (not to mention the glowing gold/orange eyes and gaunt'er faces) since only the Cyrodil vampires (Oblivion vampires) are the only ones that can look like a normal human/mer/beast because unlike the other vampires they betrayed Molag Bal and sold out to Clavicus Vile in order to be able to look like a normal person when they feed.
Its a shame they had to break the Lore for the players though...you can only imagine all the whining if they made it so you got attacked on sight no matter if you fed or not and no one would talk to you.
I don't understand this "They sold out to Clavicus."
It is not a crime to serve two Daedric princes...Molag Bal would not give a damn. They didn't betray Molag Bal at all, if anything, they are fanatics. They worship him when half the vampires out there do not honor him. Molag Bal is all about corruption and domination. You think he would give the Cyrodiilic vampires the ability to blend in order to infiltrate politics and high stations of power and influence? Nope. Each prince serves a different purpose. Cyrodiilic vampires honor Bal through domination and corruption, obviously. They dominated Cyrodiil by slaughtering all the vampire clans within their border and they worship him as their ultimate Deity, the Father of vampires. But even so, they know that they would also need to subjugate people through infiltration and the only way they could do that is to be influential nobleman and wealthy aristocrats. And Clavicus Vile was the prime Daedric Prince for this.
- Azura - avant-garde artists and visionaries that want to comprehend a beauty beyond nature and to see the future. Also, Dunmer and Khajiit.
- Boethiah - murderers, warriors, assassins, people that be willing to break the rules for greater gain. Expect Dunmer.
- Clavicus Vile - merchants and politicians; those that make their living through trade.
- Hermaeus Mora - scholars and mages that seek hidden knowledge no matter the cost.
- Hircine - Obvious one; hunters.
- Sheogorath - The insane, also obvious, though Sheogorath maybe worshipped as a god of inspiration or pain for those that brush alongside the Golden Road.
- Jyggalag - Judges? ODC-folk? I don't think this guy has a cult yet.
- Malacath - Orsimer, outcasts, victims of broken promises, and blood knights that fight for fighting's sake. Might have a following among mercenaries or marauders.
- Mehrunes Dagon - rebels, anarchists, and ambitious lordlings. If you want to topple something, Dagon is your man.
- Mephala - nobles and politicians that are machiavellian to the extreme.
- Meridia - honestly, I'd not be surprised if Meridia has a private following among Arkays or anyone that works with the dead. Like Nocturnal, she's not vicious.
- Molag Bal - sadomasochists, rapists, mobsters, those that are addicted to power and money and domination.
- Namira - The rejected, the deviant, the perverted, the iconoclasts.
- Nocturnal - Thieves, and people who have dirty little secrets or trade in them. Possibly refugees that seek a place to hide from dangers: Nocturnal is a rather decent Daedra after all.
- Peryite - radical healers, plague carriers. Anyone that works in medicine really might worship him to help understand an illness or try to appease him.
- Sanguine - hedonists or "fallen" Dibellans that live in the moment.
- Vaermina - those cursed with nightmares, or those who wish to use them to their advantage.