I dont know if he was in other movie or series but I saw Tahmoh first time in Battlestar Galactica as Helo. I think he is a great actor with good looking. He really fitted his role as Helo. At first the chrachter is not so important for the series but then with his and sharons acting, their story become second substory after Starbuck and Apollo.
I would hope to see in another good series after Battlestar Galactica but unfortunately and I dont know why? He starts acting in Dollhouse. I hope he will leave the show ASAP and get in some other good and more qualified series because I like to see him in TV but I cant stand Dollhouse unfortunately.