Dorian is easily one of the best characters in the game. His sexuality takes center stage for precisely one cutscene, it's not really a dominating aspect of his character. His alienation from is family is a dominating aspect, and his sexuality is a part of that, but it's hardly the only part.
And as for the cutscene itself, I have to applaud bioware. Including homosexuality in games is easy. Including homophobia in games is much, much harder. It's a far more nuanced and responsible depiction that DAII's approach of "everyone is bi and nobody talks about it." That approach was nice for the larger array of possibilities it opened up, but it was narratively lazy.
Incidently, I had no idea whatsoever that he was gay before playing the game.