I enjoyed playing Witchhunters a lot in TES IV and V. I'd like to suggest a different view of the class.
I have always chosen to read the name "Witchhunter" as meaning "a witch who hunts". A sort of cross between a druid and Robin Hood, with a bit of Granny Weatherwax thrown in. A guardian of The Land and wild nature. There is some support for this view in lore.
TES IV defines the class as, "Swift on foot, and clever with spells, they use distance as their ally. Slower adversaries are fodder for their arrows."
The bit about being "clever with spells" seems to fit the literary idea of a witch quite well. Conjuring a familiar to aid you is also a very witchy thing to do. Mysticism, and alchemy in the form of herb craft are suitably witchy activities, as is moving through the landscape unobserved.
In ESO I think they'd fit in very well with the Wyresses.
That quote is epic. Hmm, I didn't know that Witch Hunters in Oblivion were typically vampires.