Realistically, it doesn't make any sense for *everyone* to be bi; of course, for *some* people to be bi *does* make sense.
And that just led me to an interesting thought (though I doubt we'd see it in-game): what about bi-curious companions who ordinarily prefer one gender or the other, but are curious what it would be like with the opposite of their normal preference?
There's some curious banter in DA2. I love the banter of your companions in DA2. Bethany asks Isabella about girls and what it's like to be with one. I think Isabella is the only real bi/pansexual character in DA2. Bethany seems curious/questioning, but that at the same time comes across as a young woman who hasn't really explored anything in life, and could as well be a lesbian. I never felt that all characters in DA2 were bi. To me they were all gay and lesbian except Isabella who's pansexual. What I like about DA2 is that it allows me to fill in their orientation, except for maybe Isabella. I understand that some see it as all bi characters, but if they hadn't done it the way they did, I wouldn't have been able to fill in the blanks myself, which is ultimately what I liked about it so much.