I need a list of potential victims. This isn't a "who's your favorite follower to kill" thread as there are already a hundred of those. If someone knows a link to a completed list that would be great. Can I do in any Dawnguard followers?

Any non-essential follower.

pretty much. any follower not essential that you can take and dismiss at any time. if you don't want to kill someone you care about, go to a tavern and hire a merc follower and sacrifice them.

I found this on the http://www.uesp.net/wiki/Skyrim:Followers:

"Many temporary followers are "essential", so they cannot be killed, only incapacitated for a while. Non-essential ones will die immediately when struck down, just as ordinary NPCs. Seven permanent followers are essential as well: Derkeethus (due to a bug), Mjoll, two Dark Brotherhood Initiates, Cicero, SeranaDG and FreaDB are essential."

Everybody else is fair game to sacrifice. The page I linked also has all of the followers listed.