Bull has to walk a very careful line with the Inquisitor. He's trying to empower him, relieve stress, through powerplay. But if the Orlesian court had things like their relationship to use against the Inquisitor, he would lose face. The Inquisitor is his boss. He respects him and encourages other to by being fiercely private because it is a power issue that the Inquisitor must maintain in order to lead the Inquisition and not have his private life dragged into the mess every time someone decided to challenge him.
Dorian is not the Inquisitor. Bull treats him just like one of the guys. He teases him like he teases Krem. He's open about their relationship because it doesn't have to be a secret, it's Dorian's ego that is at stake, not the ability to lead the world away from it's own destruction.
That said, the people that Iron Bull has talked about having sex with, and the people who react to Bull, are in no way viewing him as some kind of predator. He sleeps with the serving girls by letting them "bounce on top and telling them their ****** look good." The chantry ladies were very "thankful". Bull doesn't do abusive sex that makes you feel shitty about yourself at the end of the day. He does the opposite.
Bull is not an easy match for Dorian at all. It should have been explored further, and I mean that because this: Tevinter Mage x Quinari spy/ex-spy. There is so much there that could have been very fun to explore.
Then again, Bull obviously trusts Dorian's magic if he just laughs about him lighting curtains on fire, so they don't exactly have trust issues to explore. ;_;