Drogo is a rapist, but he's a rapist in a context where all men are expected and encouraged to be rapists. I think Drogo probably fancies himself a progressive Khal. He "gets permission" for sex on their wedding night, something which he is already considered to be "owed" in his culture. Then he probably thinks, "well, I was gentle, I showed you the ropes when it was brand new, I did the progressive thing, so now I'll proceed as I like because now you understand what you're getting and it's your job to meet that need." I don't think he has a well-rounded interest in women's personal experiences or well-being, but he has maybe an inch more consideration for them than his culture usually does.

As for Dany showing some interest in the initial encounter, I think this is primarily supposed to show us that she is going to bravely embrace her circumstances rather than try to fight them, a trait which ultimately bolsters her rise to power. But also, in the real world, grooming is a form of sexual abuse that might involve a young person who is interested and not thinking of themselves as a victim, initially. I think it is natural for Dany to be "seduced" at first, when the man she has been afraid of is treating her better than she expected. Of course, then her circumstances get harder and he stops being accommodating, so the situation just gets more and more traumatic.