I was always thought the sex scenes in Mass Effect were really silly and stupid looking. And with Bioware in general it's created this really weird emphasis on the sex over everything else, as the sort of cap to all their relationships. Whereas with say, the companions in Obsidian, where some might end up possibly having sex but also others have very different climaxes to the relationship it feels a lot more balanced as a whole.
The clumsy doll-like sex scenes in Dragon Age were one of the few things that I recognised as a solid Bioware trope in that game.
Miranda's is good from a character standpoint though, even if the animation is still pretty poor. It's actually her strongest character moment really. Unlike the rest of the characters where I felt I understood the writers perfectly, hearing them describe Miranda as 'sultry' and things like that didn't chime at all with what I thought her personality was. But the exhibitionism and trophy-taking pride and need to dominate to prove herself came across really strongly in that one scene, where it felt a lot weaker and more confused in the rest of the game.