You are forgetting that while diversity is important to everybody, to some, it is also about representation.
To some, it really is important to see that they're just there, openly, and no one can give them crap about it. We are supposed to feel comfortable and to have an opportunity for escapism in games. I believe this ranks higher than having whatever a believeable character is by whomever's definition, rather than to risk alienating a considerable part of our population because there is a lingering possibility it may worsen the potential quality of the narrative in dubious ways.
(Seriously, developers have so many different ways to do that, really. I'd take a flamboyantly disco-dancing Dorian, who happens to make a gay guy with terrible taste happy, over another Grey Warden demon army any day of the week.)
The reason why we point out every gay character as "the gay character", is the same (and I do apologize for reusing that analogy) as why you would point out the one black guy in a team as "the black guy". Because it absolutely isn't pointless. Because of simple empirical deductions, you still cannot just do that. BioWare can tell you what they want, it's not normal for a reasonable amount of major characters to be gay, as it is not normal for a protagonist to be black or asian. If you do that, in glorious 2015, you have to justify yourself: "He does have a point with his dad!", "The game takes place in Asia/Ghetto Gangster environment", "She's the best ever, and super skilled. Wow, what a woman. I only say that because she clearly is doing a job that any bum of a man usually does." or "The guy is from a far away land and very mysterious"
edit: removed the original quotation, since this turned into a rather generally directed statement.