So I'v heard two voices for the Dunmer. One is rugged with an American accent, and the voice concerned here is the other diplomatic voice. Thies voice actor reminds me of the recently deceased

http://en.wikipedia.org/wiki/Andrew_Robinson_%28actor%29

who played a character on a previous show

http://images.wikia.com/memoryalpha/en/images/e/ea/Elim_Garak,_2374.jpg

When I hear that merchant in the Dunmer quarter, I can swear it's the same voice actor. Is it him?

The voice actor for the male dunmers (there's one since there aren't so many of them unlike other races) is Keith Szarabajka. He played Joshua Graham in Fallout: New Vegas - Honest Hearts DLC.