As a lesbian, I don't feel that I've gotten the 'short end of the stick.' Cassandra will be wonderful, but I don't doubt Sera and Josephine will also be wonderful. I consider Lair of the Shadow Broker to be BioWare's best DLC, and the fact that the person who wrote Liara there is writing Josephina tells me she'll be a great character.
Samantha Traynor was extremely underdeveloped though. She didn't have certain character building scenes every other LI had and had the least dialogue time, not to mention it looked like more effort was put into making her tease for male PC than into her romance.
Let's wait and see how it will look like for Josephine and especially Sera (considering that she's women-only option). I just said that both Cullen and Cassandra for now look like more significant and important characters.
BTW, sorry for off-top, but I was under the impression that you said before that you're not lesbian?