Woo! Well we got the original OP to take a breath and agree that they should give the characters a chance before judging them!
... and then we moved right on to bi-erasure! WOO HOO. And hey even a little stab at feminism too! MAN this thread is going places tonight. 
Being "not all that talkative" about who you'd think would be fun to climb into bed with does in no way cheapen a character. OR A PERSON. Sometimes people and characters alike aren't all that comfortable shouting who makes their naughty bits quiver from the rooftops.That doesn't make them less. It just makes them a bit shy.
Merrill is Bi. Fenris is Bi. Anders is Pan. Isabela is Bi.Each of them are different in how they express their multisexualism. That's not only a REAL THING, but it's also a REAL THING that fictional characters can do! It's also not at all strange to have a group of not-straight-people hanging out together! In fact it's about as not-strange as having a bunch of straight people hang out together!
and now I'm cranky. I'm taking my random sword sticking out of the Hanged Man's floor and going home 