Excuse me while I prove each and every point you made completely wrong.
On the dawnguard order side we have an Ancient looking order that has APPEARED FROM NOWHERE and has never been mentioned before. Furthermore there are already Orders dedicating to fighting undead.
First off do you expect to here about every ancient order in existance? No. There isn't a big book of everything that exists in the elderscrolls universe. Just because its an ancient order doesn't mean every peon knows about it.
Firstly skyrim's Main Group of vampires are the Volkihair . Who Live (or stay dead, whatever) underneath Frozen lakes. They are basicaly "ice vampires" and so probably look like Drowned corpses covered in frost. Not a bunch of Fancy people living in an island castle (which might be akaviri).
FACT: Your source on Volkihair's abilities is from a book Immortal Blood the author a vampire. Give me one good reason that source is trustworthy. Why the hell people continue to rely on that piece of garbage is beyond me. There is no reason save gullibility to believe a book about vampires abilities when the author is a vampire. So this entire claim is moot as you have no evidence to support Volkihairs have the abilities you think they do because your source is a vampire.
Secondly the bat magic- What a horrible cliche that doesn't fit with the magical rules of Tamriel . You Summon spirits or Daedra- Not small and fluffy animals! It does look nice but so do shiney things.
Oh really available summons in Morrowind included Centurion Sphere, Bear and Wolf. In Oblivion with the spell tomes download you could summon a bear. So your claim you can only summon daedra and spirits is also complete [censored].
The werewolf like transformation is also a Non tes thing. It's like they just ripped ideas of a movie to be Epic and hip.
They had werewolves in Morrowind and in Daggerfall.(along with a few other varieties) So your claim that lycanthropy is not a TES thing is based in ignorance. However I assume your talking about the monsterious vampire lord transformation that actually goes back a long way in literature about vampires. Plenty of classical tales feature vampries transforming into demonic creatures.