I must agree on this one, as much as I love this character, there's just so much weakness to it writing-wise. The problem with the breakup was that it happened so anticlimactically in a hurried 3-line conversation, that felt more like a planned betrayal from him, even though I was supposed to believe he was acting out of his strong sense of duty. When he does the US for his love, there's real catharsis, but this scene is just maddening and a spit in the players face from the writers, because if you play with a female warden they practically trick you into romancing him, it's just so hard to avoid those conversation options, and you feel like this love is as important part of the game as the main story, and for him the warden means a great deal, certainly more than being a popular king and securing the bloodline.
but the real crime against his character from the writers part is the whole "hardening", why is there even such a thing? and the complete personality change hangs on one conversation line? I would have been so much happier with his character if it happens throughout the game and the warden's choices during our conversations, not in that completely unrelated one-time dialogue. I like his hardened personality much more at the end of the game, basically every time he raises his voice I'm glad because that's what I expect from him even if he remains a warden, to grow up, take responsibility and sand up for his beliefs. Sure I love his jokes and awkwardness too, but that whining on the Landsmeet and after that is just unacceptable 
also it was so weird after 3 female warden playthrough to play as a male noble. I had a really hard time trying to be best friends with him because it was so much harder to choose the empathic options after I have lost my entire family and lands. and our friendship is supposed to be about me consoling him about the loss of Duncan? it was easier for a female even if I was a Cousland, but two grown man sobbing in front of Flemeth's hut just felt so pathetic. I wish there was another route to gain his trust without having to always give in to my feminine side as a man.
Anora - I understand her motives too, and I can imagine her being a great queen, but I despise this kind of political character in general, and what makes me hate her even more is that she can come off as a genuinely positive and trustworthy character if I agree to support her and don't make that mistake with that line about Loghain's fate. So what bother's me is that she doesn't have a stable personality from the player's viewpoint through various playthroughs, she can be a great ally and a wonderful, good queen or an oppurtunist shrew, maybe it's brilliant from the writers, but it just drives me mad
So I rather make Ali king (always hardened, even though I hate the method) and if I live, remain with him as queen or at least a chancellor.
The hardening is meant to be a character arc. And if you know anything about character arcs it is that they occur over a period of time and you see it happening gradually so it has almost a cathartic feel. Loghain seems to have a better one if you pay attention... how he starts so bold and sure he is right to gradually becoming more disgusted about actions he has to take like when he agrees to Zevran and then he looks defeated and like he has failed the world when he's sitting in that chair. He still has fight in him though. He will fight to the end and when you defeat him that is the completion of his arc. It's not a perfect arc but it's better than Alistair's where Alistair has behaviors that don't make any sense and half of them hinge on one line. That is just bad writing. Writing should mimic reality, how people really act, things that might really change them and HOW they would change as well as the extent to which they would change from whatever the impetus behind those changes. You saying one line to him is simply not enough. It's a game mechanic that fails. The only way it would really work is if seeds were planted all throughout the many conversations you had with him during the game. Try doing what they did here (hardening) in a movie or tv show and you will have an epic fail that people will find false and probably say the movie or show sucked as a result. It's actually an insult to gamers that the writers feel people will buy it lock, stock and barrel. I get that it is a game but if they are going to employ such a tactic, it should be soundly written and look like it makes sense to any reasonable person, and yet, a lot of people find it to be 'off' for lack of better words.
Now, if they added more conversations where you shape him with your opinion on things... conversations that show because you are his leader he looks to you for guidance even if he doesn't agree with your choices though that I think could trigger something entirely different. If he doesn't respect your choices then he does the opposite of what you say and that creates a different arc. But it is a game and they wanted all the variables in the outcomes, and they wanted it to be easy... take him to visit his sister and poof - he's hardened where that should have been a defining moment only after some other conversations that lead toward that outcome. There should have been a logical flow. Sort of how, if you play ME, you can sway garrus toward renegade/spectre or paragon/csec. That was done well and clearly Drew is the superior writer in those matters. Not that it makes much difference in ME2 but there is some difference. But they use this ONE magical sentence that makes no sense at all to trigger a bunch of changes. Then they use the taint as an excuse. Also I think a huge part of it is that it was written by a man or by men. They are clueless about these things. This is how they would behave or how they think it would make sense to behave under these conditions. I guess they have some understanding of how a man would be since they are men, but I think they failed to factor in some of Alistairs other traits along the way. Like the make such a big point of how he wants to be loved. That is the most essential piece of his being and he easily tosses it away under the right circumstances or perhaps the wrong ones. I don't know what kind of a wuss you have to be to finally have the one thing you always wanted and then so willingly almost wantingly give it up. Sure he isn't coming across like he's happy about it, but if you harden him he does it as well under the right circumstances. So it's not just when he's a wuss who doesn't stand up for himself. It's when he decides to stand up for himself that he crosses the very same line unless you make the right choices.
That's why he should never be king. If he cannot even be firm on staying with the first woman he had sex with, the first woman he ever loved where he actually tells you if you persuade him to come to your tent before he asks you that he didn't think he could feel that way or even find a woman he cared enough about ... well that's quite the thing to just give up so willingly. It turns him into a raging victim who doesn't take control over anything, which given that if he romanced you and did ask you to sleep with him, that is clearly not who he is. He has evolved at least enough to take initiative in going after what he really wants despite he might be rejected. That is huge for someone like him. That is an arc that should make him stay with you no matter what. It is illogical that he would achieve love only to give it up so easily. People who get what they really want do not willingly give it up so easily, especially when they worked for it and even more so if it is not being taken. There is no logical reason behind it at all. From a psychological standpoint, it makes no sense and clearly the writers have only a very juvenille understanding of what drives people to do what they do (which for the most part there are things that are fairly consistent among all people no matter their history or beliefs and one of them is they don't so willingly give up something they really wanted for so very long when they finally get it. Actually, in some cases they would go to great extremes to keep it even if they are a wuss. In fact, if they are a wuss, it's more likely that their nature would be so conflicted they would become rash to keep it unless they are so steeped in being a victim that they just didn't think they could have it... but that only applies if the person wants to leave them or if it is being forcibly taken away in a manner that they feel powerless to fight against it. But it is his choice and nobody is pressuring him to do it. So he is just willingly giving you up with some weird logic to back it)
The writers just never really thought any of this through. They didn't take time to consider the psychology behind any of it and they just focused on their little flow charts. Fine if that's what they want but then the writing has to work with the actions that follow or else it falls to pieces. You have to see hints of this coming. It has to be foreshadowed rather than 'oops, suprise... '
As for playing a noble male, I realized a bit ago that the game is designed so that as a male odds are that you will screw him over. As a non noble male, you might befriend him but his personality is such that it will be hard to do so. I didn't care for him one bit as a male. I saw him as a very annoying person. I had more respect for what loghain was trying to do even if wildly misled than I did for Alistiar who just complains and whines the whole time though if you are romancing him, you don't see it as that so much but when he gives you that flower the writers acknowledge how they have made him only as a woman romancing him, you look past it to see the kindness and goodness in him and you can empathize where he has been and what he survived. Only my most hardcore PCs tend to see him as weak. They are Xena types - tough as nails though. Not a whole lot of compassion. Just razor edges to them and their personality. Xena before she became good but not at her worst.
And Anora, as much as it seems like it is a different side of her, I still think it's the complexity of her. What woman who adores her father, which she clearly does and clearly still sees him as the hero who made some major missteps, would allow him to die? There's a bit of that nobility above it all mixed in there where she feels he should not have to pay but it's also a girl protecting her father. I'd be stunned if she agreed. At least she is loyal to someone. Frankly, I kind of like that about her. She agrees what he did is wrong but she doesn't want him to die for it and certainly not to die disgraced when he did save ferelden from Orlais. You don't see that about her if you don't have that conversation because she has no reason to think he will be killed. Again, it's that noble holier than thou attitude that you see with Vaughn as well. They think they have a right to get away with whatever they do. She expects he will walk free or at least not be killed. She was raised entitled and that is her thinking. Nobody is going to interfere with that. Nobody will interfere with any of her plans. That is what you see from her when you make different decisions and when you talk with loghain if you spare him.