http://skyrim.nexusmods.com/mods/21615
I'm considering delving in to "neuter" the spawns as well, but I think it may be harder than it looks because of the conspicuous lack of official modding support for Dawnguard (IE: no papyrus source code files).
Thanks for the link! Not too sure how I feel about that mod since it sounds like it's got potential for corruption or system slow-down if it's constantly resetting the script, but I'll give it a shot.
Hmm....couldn't you just go into each NPC that spawns in the attacks, edit their values(like give them 1 health) and neuter them that way? No papyrus required?