IRON BULL SURE DOES!!! First trope up there. Leliana herself does! She herself is Isabela, but retired version with Chantry sister's clothing on her. She herself was wild during her bard days and she herself will gladly accept foursome with Isabela and Zevran as well. If you harden her, she will be willing to fuck Zevran, even though she is in romance with Warden, if other didn't 'wuss out' of it. She herself falls into category of: >all bi people will fuck whatever it moves and offers as they got no morals and understandings of how serious relationships work
Josie, I agree. Ok. Gonna admit there is exception on that one at least. But, she is hardly something, considering her role is barely anything. She falls into complete background among new characters. Romancing her was like romancing Samantha from ME3. It was nice and sweet, but it didn't had as same impact as romancing Liara did.
As for rest: Merril, Anders and Fenris I don't count as 'true bi' characters, since everyone in DA2 was one.
I mentioned Isabela because she was one in original too. Anders... I won't say he was ever 'the most straight guy out there', but Anders in DA:A never shown interest for cock, even for a second. In fact, he constantly was talking about girls, hitting on them and he was even 'hitting on' Andraste's statue itself. Wondering was she truly this HOT in reality too. So, I ain't gonna debate if DA:A was 100.0% straight, but, he certainly showed only interest in girls. While DA2 Anders is inverse. He is more cock-friendly than vagina-friendly! I dare saying that BW originally wanted to have him be just gay in DA2, but decided to go bi route instead. Either because 'gay Anders' would contradict one from original who was vagina-obsessed instead. Or, because they made everyone bi to start with! Not gonna count DLC Sebastian thing that was apparently locked only for females(straight), because I never gave a crap for him or his DLC enough to check it out.