It's a start. But obviously the majority of named NPCs aren't covered by that.

Well, I have 104 separate voice folders extracted from the BSA, and there are errr... 71 people on that list. Now the guy who did specialmaleuniquetsun also did the malenord, and they're two separate folders. I don't know how much more overlap there is, and one actor or actress may voice for a heckuva lotta characters (for instance, Joan Allen does the voices in the femalecommander folder, which covers Rikke, Adrienne, Aela, Zaria, Thane Bryling, Housecarls Faleen and Iona, and Jarls Elisif, Laila Law-Giver, Idgrod Ravencrone, and Brina Merilis - not to mention The Wolf Queen Potema and the bloodthirsty witch at the beginning who wants yer head off!)
in other words, I think it's mostly covered.

Edit: See also: http://www.uesp.net/wiki/Skyrim:Voice_Actors There's 81 actors on that list.