Not unlike the Solas romance. That one tops the emotionally unhealthy and destructive rankings.
I agree when it comes to real life, but it's fiction. What point would there be to the story if there's no conflict?
Drama is a chance to explore the personalities of different characters and how they clash. It can reveal faces of a character you've never seen. It's a battle of wills, wits, and words. If we took all the dramatic realtionships out of literature, because they're not right and shouldn't be happening, many, many good works would be lost.
Not saying everyone should be playing rivalmances, but I just don't agree with the idea that it's unhealthy for the character, so it shouldn't happen. I wouldn't read/watch/play something where they brush their teeth, go to the gym, and have polite conversations over a balanced meal.
DA2 "Rivalmance" is nothing but the ability to roleplay an emotional abuser who can insult, humiliate, belittle, undermine, patronize, mistreat, and sabotage their partner with impunity, since said partner just keeps coming back for more (even though they obviously look angry, miserable or frustrated over it) and fawning over you and putting out for you anyway. What a valuable roleplay experience. 
In real life, I was an a relationship similar to Merrill's "Rivalmance" where I was the Merrill, not the Hawke. It was not fun. It messed me up very badly emotionally, and I didn't realize until later that I always felt miserable and invalidated and was an emotional wreck toward the end because partner was emotionally abusive.
The fact that BioWare presented that kind of relationship in a video game with the player as the abuser and tried to pass it off as "still healthy, even though you disagree" is honestly disgusting to me. (It's all good and well for you to say "That relationship is not so bad" when you're the Hawke, but not when you're the Merrill.)
I also never said "no drama ever" or that I thought the Solas romance was 100% healthy or without problem, but at least it doesn't glorify abuse.