Yes, that's an important difference: Dorothea loses faith in Casaubon's entire project, whereas Finduilas continues to believe in Gondor, but doesn't think it's going to survive.

Perhaps the Finduilas Happy Ending Story has Denethor expiring?

That's sad :-(

I think I am more positive about Boromir's Stewardship than you are, particularly with Faramir as chief sidekick. What worries you about it?