For me, the banter is waving the Very Much Not A Healthy Start to a relationship flag, and unfortunately triggers some alarm bells for something that could very easily turn emotionally abusive. A relationship that starts on sexual harassment, disrespect and constant boundary crossing is a bit of a gut punch after what Dorian went through on his personal quest. I wouldn't have been quite so shocked if there had even a line of banter from Bull to Dorian at the end - 'Hey, Dorian, I think I've been making you uncomfortable, and I get that. I'll respect your wishes, and keep it between us from now on' would have showed some growth and understanding. Some much needed respect for Dorian, as well.
Yes, Dorian does have many snarky and disrespectful things to say to Bull, but he keeps the sexual aspect away from it. I still feel it's a constant power game between them that Dorian never wins, and it's not an equal back and forth. While that aligns with Bull's character and his backstory, I really, really don't think it was handled well for something we just hear snippets of in the background.
A good example of equal verbal back and forth for me is Dorian and Blackwall. They're pretty horrible to each other. (I'm not even sure who started it. Blackwall never has positive things to say about Dorian when you ask about your companions, but Dorian seems to be referring to him in various unflattering ways from the get go.) After their personal quests, they finally seem to get a good understanding on each other and apologise. It's the resolution that makes it work, there's an arc. Dorian isn't comfortable with Bull's banter, and while he may respond positively in private, is not something we see as a player. It's opened-ended, and since is intended to be potentially unhealthy, you can understand why a lot of players would feel uncomfortable.
A cutscene or a few extra or changed lines of banter could have gone a long way. (Bonding and snarking at the bar, or something.) I really do understand where people are coming from in disagreeing that the banter is an issue, and think it's just a back and forth between them. Yet, I think the writers had such a fine line to walk with Dorian and Bull, and they weren't able to do it properly. I know both characters have been through a lot, and it would never have been as easy relationship, but I think a different route, with less accidental abusive overtones, would have been more appropriate. Bull's behaviour is pretty insidious, and it made me do a double-take on Bull and the Inquisitor as well.