I dunno...Mixed feelings on this one. She got a lame death because she wanted out of her contract or something...but she also didn't get to develop that character as far as it should have been.
Story I heard was that she wanted out because she didn't like how her character was developing (or, more accurately, the lack of any development). So she managed to convince Roddenberry and others to let her go. Which is a shame, because Yar did have some potential, and if Crosby had stuck it out for another year or two, she might have seen more development once writers like Michael Pillar took over.