The way I see it, Dorian and the Inquisitor need completely different things. Maybe what Dorian needs is someone who isn't ashamed of being with him, who isn't willing to keep things a dirty little secret, and who is proud of what they do together. Dorian clutches his pearls and acts loudly ashamed of it, but in the same banter where he is acting ashamed, he finishes it up with "If you insist on leaving your door unlocked like a savage, I may or may not come." So it's pretty clear at that point that while he is struggling with the idea of their relationship being visible, he's working through it. If he told Bull to be silent and stop because he didn't want people to know, Bull undoubtedly would (and probably cut off the sex entirely as he does with the Inquisitor), but for now Iron Bull is pushing him because Dorian struggles with being ashamed of his wants/needs and that is the best way Iron Bull can help -- force it out into the open, and let Dorian see that the world isn't going to implode around him if he has a relationship with someone publically.
I think the pearl-clutching is more of an act or else Iron Bull wouldn't be so convinced that Dorian is a great guy, right? If Dorian was actually that ashamed of Iron Bull, I don't think that he would stick around. (He doesn't stick around if the Inquisitor is ashamed of him when Cassandra, Cullen and Josephine walk in, for instance. Bull is very comfortable with himself. I don't think he'd let himself be degraded into being a sex toy, the same way Dorian is fully capable of standing up to the Inquisitor and walking away when they do things he doesn't like.)
So yeah, Bioware did have to write it in a way that forces them to go public, or else we the players would never have the first clue what was going on if Iron Bull was as secritive as he is with the Inquisitor, haha. So they could have added a few more lines to smooth things all out and clarify for us, the player. As it is now, David Gaider made it clear that both Iron Bull and Dorian are fully consenting adults, and that Dorian's discomfort is simply in that he's sleeping with a big brutish Qunari when he's so determined to appear high class and sophisticated, the same way he doesn't want to admit that he enjoys Ferelden Beer because a finely bred Vint such as himself would only enjoy the finest wines, amirite?
So nothing overly harmless, a few things that could have been clarified with a bit more dialogue, but there's nothing we can do about that except headcannon it out and write lovely, lovely fanfiction.
I refuse to let other's negitive headcannons ruin the fact that we have a Tevinter Mage and a Qunari Spy overcoming their differences to have an open, homosexual relationship that begins rocky (Duh, Tevinter Mage and Qunari Spy, right?) but ends up being something big and special between the two of them. ♥ It's huge that we finally have a canon homosexual relationship, and since it's between two sexy characters I really like, I'm willing to overcome my jealousy and let them be happy in my head cannons. (My Inquisitor is totally making a Quizzie Sandwhich with the two of them though.
)
I don't think it reflects negitively on either character. They have a lot against them as far as background, upbringings, pre-conceptions and emotional baggage, but they work through that to find happiness with each other. It's Romeo and Juliet, Dragon Age style.