I came here tricked by the "roman" in the title, but it's OK, the thread touches a few of the reasons why I think romances in Bioware games have the quality of a teen tv series.
In DAII I've only tried Anders. I remember a particular scene that reminded me why I tend to ignore romances. Anders wants to move to my place, I'm obviously not too fond of the idea, but Hawke can only answser with "no" (a broken heart) or "yes", which when spoken turns out to be something like "I love you so much we're going to live together forever". Riiiiiight.
So to the OP's points 2 and 3 I say yes. The romances need something to be less shallow. In my opinion those highs and lows should be intertwined with the main story, the romance should be part of the main story and not the side quest feeling they have now. One romance I felt that did this right was Bastila in Kotor. Anders and Alistair have some of that as well, unfortunately there was all that Twlight dialogue in between that I couldn't get past. But the rest of the romances, filler, side quests.
And with this, to the first point I say no. Or yes, if we can't romance party memebers. In my opinion the way to make romances better is to make fewer but more relevant. One man, one woman, the content of 4 concentrated in 2, with the main story turning out differently depending on whether you've romanced that person or not. That's the only way the romances would redeem themselves in my eyes and I'd be tempted to try them again.