I can only speak for Halsin's ending but there is litteraly no logical narrative reason for it. Especially if you solomanced him. Ive used the phrase bait and switch in his threads and I think it is very appropriate for his ending.
Its not just I wont get my happily ever after with him. It was just bad writing, along with all of his other issues that we've gone over in his two threads.
I dont think there would be as much complaining if it was just a simple "But I diddnt want a sad ending."
Tragic, bittersweet endings can still be gratifying and appropriate even though they may be painful for us as an audience due to the emotional attachment to the characters. Old Yeller is a classic example of this. While tragic and sad, the way the story was written it made perfect sense that the events happened as they did which is what made the emotional blow so hard to take. But its still a beloved classic story, and I dont know about others but I dont want to change that ending because it was a good thematically appropriate ending, though painful.
Im not 100% sure that that is whats happening with these characters though.
