I'm not commenting on how good/bad DA2 was...I don't think it matters here.
Indeed. I don't think whatever they did with DA2 does not matter at all - or, only as example how you should not do it. Therefore I think your bringing it into the discussion was pointless in the first place. It's irrelevant how romance was handled there.
You see, the trick is not to give people what they say they want. That's impossible and in many wouldn't turn out as they think they would. So now you can screw Kira. What changes it? Nothing, it's still the same Kira and the game doesn't change besides a few minutes of dialogue. It's not the same as when it becomes part of the process of rising in level and exploring the galaxy. The trick is to give people what they would like
The primary reason I can imagine why people would be averse to companions that don't belong to a particular class is that people like things for themselves in the first place, not for everyone else. Like it was a property and they don't wish to share it. Like the experience of a companion character becomes more enjoyable the less players are able to share it. I don't think that's the case, though. People would enjoy it or not, regardless who else can do the same.