Would have been better if Cassandra represented us, then I would have given Bioware props, but I don't really give them props for Sera as far as representation. If you were someone who had no prior knowledge to the fact that she was gender gated, would you ever actually know she was a lesbian? If you were a male PC for all you know she could just not be romancable like Vivienne, and if you were a female PC, her dialogue could be completely interchangeable with a male PC with some changed pronouns. That's the problem. The meta knowledge that she's gay is supposed to be enough, but it's not.
My thoughts exactly. There was a lot of hype that now, with LIs having different orientations it would finally matter. Of course, it could only matter for non-straight folks because everyone is expected to be straight by default, it's considered to be the "norm". And it did matter for Dorian, but as for Sera, not at all. She could as well not be a lesbian, if she was turned into bisexual there wouldn't even be a need for much change in her conversations. Her orientation doesn't play absolutely any importance in her character arc, because of what I don't find her believeable.
I know that some people think that it would be better if we pretended that we are the same, statements that "why should it matter that she's gay, other characters are straight and no one makes a fuss of it", but it's a lot more complicated, and our situations are not symmetrical at all. Simply because we're members of minority it affects our lives from the moment we realize that we're different. And unlike racial or ethnic minorities, we're not born among people who are like us, we can't stick to them (though thanks to internet things are a bit better nowadays), and surrounded by people who aren't like us, we think that something is wrong with us. Google the concept of "heteronormativity". It would have to leave an impact on Sera.
Of course Thedas is not medieval or later Europe, it wouldn't make her think Maker hates her and she will have a gruesome death if anyone finds out but it was clearly showed by codex entries that it's not considered to be something "normal". So, it appears to be similar to how homosexuality is treated for example in Japan. And no, it's not the same as heterosexuality.
I was wondering if it's because Dorian is written by a gay man and Sera is not written by a lesbian, but then I remembered that some of the classic lesbian movies like F***ing Åmål/Show Me Love were made by straight men, and as for games, Gone Home's story was written when the studio was composed from 2 straight men and straight woman (later a gay woman joined the team but according to the site's info she's responsible for technical stuff), so it really wasn't impossible thing to do.
So personally to me it feels like we've got short end of the stick again. Gay men having this wonderfully developed character with much importance to the main story, whose orientation, while doesn't define him and isn't everything he is, is part of him and is not not pretended to be something unimportant, giving gay guys visibility and representation. Sera is none of it, you could easily never see her face and she was intentionally made as polarizing character as possible so devs knowing it give you an option to kick her (and only her) out whenever you want.