I agree that they handled Fenris's mage romance very well. I'm a Fenmancer in DA2 and my favourite game is a rivalry mage romance with Fenris. My only problem with it really is that intellectually I don't buy it. Fenris is damaged and stays damaged by his experiences (which strangely enough is part of the reason I like him so much, I hate the whole my lover will CHANGE because of me dynamic in games. I've never changed for anyone and I don't think many people actually do in a substantial and enduring fashion because they fall in love with someone else) and I can see him getting over things enough to work with and respect Mage Hawke but I just can't see him jumping into bed with them and coming back. Maybe the sex but not the return.
I don't want to make this about Fenris since this is the Cullen thread, but I want to say I respect your opinion on the romance
I'd only add that to me it's not about changing or curing him (which I agree is a gross and awful concept) but more about showing him that he doesn't have to fear Hawke. And for Hawke to acknowledge his fears and his past, and if Fenris can see that Hawke isn't Danarius or any other "evil" mage he's met, then in a way, that's almost like a sort of healing.
I've always thought Cullen's and Fenris' issues were different though, because Fenris comes at the issue from the point of view of a slave who was abused by magic, whereas Cullen comes at the issue from the point of view of a person in a position of power who was tortured for a short time (in COMPARISON to Fenris' whole life) by those he was supposed to hold power over.
So although I don't advocate magically healing Cullen with our super vaginas/dicks of Perfect Love, I think the romance between Cullen and a mage is less complicated.