Lots of posts since I went to work!
About the line in Dorian's personal quest ("I've more than just heard about it, actually"), and Halward going "Oh so that's why!" I took it to mean he was insinuating that Dorian was having sex with the Inq at that point, and that's why he's joined the Inquisition. As I recall, Dorian's line is "No, you don't get to make those assumptions about him." It definitely comes across as very defensive there, he doesn't want his father assuming they're sleeping together, or that Dorian is using him, or the negativity that'd come from it if they were. Dorian later says he doesn't care what people think about *him*, he cares what people think about "us," and thus, the Inq.
My rogue thinks it's pretty adorable that Dorian wants to protect him, even tho he truly doesn't care what people think of it. My mage, being a bit more bashful in that regard, would appreciate it more. My warrior, given the option, would probably be like "lol let them say it to my face if they have a problem."
Probably the only way I won't romance him is playing a female character. Taking a break for WoW right now tho ;p