I'm inclined to agree that Sela is not that great of a character, and Tomalok was a good alternative in "Redemption." One reason I consider "Yesterday's Enterprise" my favorite TNG ep is that the writing was so strong. We got to see the sort of Tasha Yar who would have made a cool regular, who seemed well developed compared to how she was used in some of the S1 eps. It always impresses me how well written Tasha is in this ep, even though her "revival" is short and ultimately temporary. Letting her die honorably is a great component of the story.