I don't have strong feelings about Sela, but the possibility she caused less Tomalak appearances makes me dislike her.
You've got it backwards. Andreas Katsulas would never have played Sela's part, because Mr. Katsulas didn't think Tomalak worked as a character when he was standing next to the protagonists. He thought Tomalak was best as a menacing, larger-than-life figure on the view screen.
"Future Imperfect" was the only exception to that, and you'll note it was his last appearance in the show until AGT.