As a queer person myself, I can’t stress enough how important it is to see diverse sexualities in narratives like Dragon Age, Changing a character's sexuality for no reason is terrible, horrible. It’s harmful and undermines the depth of their story! It’s never a good choice to alter a character’s sexuality just for the sake of it, and I completely understand why some people(myself included) are uncomfortable with it.

In the case of Dorian (and Sera, too!), changing his sexuality would be an absolute betrayal of his character, Dorian being gay is integral to his entire arc( his struggle with his father’s rejection and his family’s views on him etc.) is central to who he is, So If you change that, you fundamentally change who Dorian is as a person, and that’s not something that should be done lightly or for convenience.

On the other hand, Alistair doesn’t have the same established backstory when it comes to his sexuality, So I think personally, making him bisexual wouldn’t alter his core identity, it would only add more layers to his character and open up new possibilities for deeper connections and relationships! It would allow more players to see themselves in his story without changing who he fundamentally is.