Indeed, I thought so. It's my main complaint with the way the DR and its consequences were handled. Kieran with a god-soul would've been infinitely more interesting, but I guess they didn't want to tell more stories about him, so he became normal and now they can forget him.
It's more like people expected him to have a pivotal role at some point, and he can't. Not everyone did the DR. In fact, it was hotly contested then, I know, I was in on that conversation, or rather, those conversations. The only way to make him relevant would be to canonize the DR, and that would alienate a lot of people too.
My canon Warden didn't refuse the DR due to any real distrust of Morrigan, but because once she learned what would happen if she took the killing blow, she decided that that was her "out". Alistair crapped on her on the way to Redcliffe, accusing her of something to cover his lies. A lie of omission is still a lie. Then he stormed off to be a drunk, or maybe died. I didn't want Loghain to pass the Joining and then get an easy out from his crimes, so she went for the US. She didn't want to survive the encounter. She actually didn't want to save Denerim, but the game didn't give her that option. Why would a CE care if the Shems burned, after all? It's not like they were exceptionally kind to her people before the Blight, and it's not like anything was going to change after, so why not fortify the Alienage, and let the rest of the city burn?
At any rate, the US was chosen not because of Morrigan, but because of the way the game "treated" her on her journey to the final fight. She saved as many of her people as she could, and ended the AD and herself, so that she wouldn't have to deal with the crap any more. Then people wanted to canonize the DR, taking away all the meaningful things I accomplished with my US ending, so that they could, in the words of another poster, have sex and live. No thanks, it's not like she was even going to be the one having sex, Loghain would have.