We had one of these threads a couple of weeks ago... at least this one is a bit more reasonable in tone but I don't see why you can't ask for less tragedy in romances without adding the "and can't you stick it to the straight guys more" as well. Not that I mind actually, tragic romance stories can be quite moving, but first they would have to create a female romance I actually care about and I'm not sure that's allowed anymore.
It's less that I want to foist it all off on the males as that I would prefer to see it evenly distributed, if there absolutely must be heartbreakers in the games. I'm all for less heartbreak overall. I don't hate tragedy, as I explained in various posts. I'm okay with there being an occasional tragedy. However, it's not evenly distributed currently, and there's far too much of it in the games that is inevitable, no matter what choices you make or what you say to the LI.
One of the biggest problems, though, is that it's usually a male LI and it's usually unavoidable, or else it takes a tremendous amount of choices to avoid. While choices are great in a BioWare game, why is there nothing similar to Alistair among female LIs?
At the very least, if every other male LI must be a heartbreaker in some way or another (I avoid saying tragic because it implies death), make it possible for most of those events to be avoided, and don't make it ridiculously difficult to do so. Would I like to work for my happy ending? Yes... but I don't want it to be nearly impossible based on what choice I made in a very early quest or dialogue. Do I think some stories probably should end in inevitable heartbreak? Also yes, but to be honest, it'd be nice if the romance could end well even if the overall story outside of the romance does not.
I'm okay with some tragedy if the romance has a happy ending. As many of you already said, Morrigan is a great example, and it is no wonder she is one of fan's favourites character. She has many layers and she grows over time, which is a beautiful thing. Players were left bitter when she left, but were given the chance to end up with her anyway in a DLC.
Choice is what matters here. You want a tragic ending for your LI? Sure, Alistair could break up with you, or one of you could sacrifice for the greater good, even if still in a romance. That's perfectly fine. But you also had the option to be happy with him in the end.
DA writers know how to handle choice, they do. That's why I would be so disappointed if all of a sudden they took that away from us. And I'm not talking about "good" or "bad" choices. I don't want to burn up the world to be with Solas again, I want my Lavellan to be able to be happy with him without feeling s*** about it. I like how bittersweet Solas' romance can be so far, but it's because I hope know it's not the end of it. If it really ended like that I would just be pissed and I wouldn't want to do it ever again.
So, yes. Please, I can't handle tragedy in a romance if it's inevitable.
Morrigan is less tragedy, more heartbreak. She doesn't die, after all. And as you pointed out, players who chose to romance her still have agency, because they can buy the DLC and conclude her romance on a happy note.
I agree that choice is a big factor, especially since BioWare pushes choice as the most important aspect of their RPGs.
As for Alistair, the option to be happy with him in the end wasn't an option for mage or nonhuman Wardens who didn't harden him or become Wardens with him--and hardening his personality isn't something a lot of people probably did, in their first playthroughs. Also, many would argue that being someone's mistress is not a happy ending, or that leaving Anora queen alone if you're an elf (because you ran off with Warden-Alistair), or forcing Alistair through the Dark Ritual in any situation, wasn't a happy ending. And then you might have to choose between Alistair or Hawke later on, which would be an agonizing choice for a player who romanced Alistair but who genuinely enjoyed playing as Hawke. So having a happy ending with Alistair is just TOO difficult. I don't mind some difficulty and I don't mind hard choices, but there is no equivalent for a female LI to the number of specific choices that must be made for Alistair's romance to have a happy ending.
If Solas doesn't get a special DLC about him reuniting with Lavellan the way Morrigan romancers got Witch Hunt... >_>
I actually enjoy tragic romance quite a bit. I thought Solas's romance plot was AMAZING even though I am still hoping for closure via DLC.
Cullen's romance hit the sweet spot for me; just enough conflict with the lyrium addiction subplot to keep it from getting boring without going overboard. I haven't done Bull's romance yet but I hear good things about that one too.
What bothered me the most about Alistair's romance was the fact that I had to let him sleep with Morrigan. I was playing as a mage. I didn't HAVE to put him on the throne, but I chose to do it (and remain his mistress). I was OK with that part, but I definitely understand why other women would not be. Having to convince him to have sex with Morrigan was awful. Yes, I'm bitter, and I want the straight male players to have to sit through something like that. If they did, perhaps the uproar would be enough to prevent such a storyline from ever happening again? 
Making it possible for Cassandra to leave the player if she becomes Divine came pretty close to a tragic romance for straight guys, but it's possible to pick dialogue options that leave the fate of your relationship open-ended, where for female players' tragic romances, this has never been an option.
I can't think of a single romancer audience that is clamoring for tragic romances, so perhaps they should be avoided altogether? Straight women are unhappy, and straight men and LGBT players don't want the tragedy foisted on them instead. If there must be a tragic romance, make it between NPCs so that the player is not personally affected by it.
I don't think tragedy or heartbreak should be avoided altogether. Sometimes, it does make for an excellent story. Some people do genuinely enjoy those kinds of stories. I don't want to be the person who causes something enjoyable to be taken away from other people.
My solution is to spread it around more equally and give the player agency over whether or not most romances end in heartbreak. Sure, one or two across 4 games who led to inevitable, foreshadowed, heartbreak would be fine. But don't always make it the male LIs who have these inevitable heartbreaks ahead. And, let the others who have potential heartbreak in the future be influenced by the player's decisions--though let's not make it quite as difficult to get the happy ending as Alistair's, shall we? Because that one is pretty much to the level that it's ridiculous and nigh-inevitable.
I'm on board here I agree with you OP and I want to get permission to post the link to this thread to a few people at BW on twitter.
Tis okay with you? 
I'm an optimistic person but I don't mind a little drama in a romance as long as it has a happy ending. This giving straight ladies a tragic ending constantly is getting really old and a lot of ladies including myself are getting tired/sick of it. Thane,Anders,now Solas... *sigh*. 
I don't mind the link being tweeted. I suspect they do read the feedback board, but directing them to it cannot hurt.