Well, I just finished my Twilight of the Arnor campaign and I have to say that was the silliest, most underwhelming finale I've ever seen. It seemed like there were two ways to win: The traditional way and the perceptive, five-minute way.
Apocalypse looked like a neat remix of an earlier scenario: Get to the other side of this map as fast as you can. Unlike the previous one, you needed to blow through a determined Dread Lords defense once you got there. I look at my tech tree and it's full of shiny new techs. Oh frabjous joy! Since my life support isn't maxed out, I'll trade with some other factions for planets.
The instant my Arnorian ships get to the other side of the map, they hit Du'toth and a transport follows it up. Scenario over.
Nightmare is even worse. You need to research 20k research points worth of Terror Star techs. But what's this? Your neighbor the Iconians has all of them? And you have a handful of expensive, incredibly powerful ships? Swap out, rush-build some constructors, put together your Terror Star on Turn 5 right next to the sun, and you're good to go.
I think those scenarios, combined, took all of 10 minutes. Were they supposed to have a secret instant-victory path, or was that accidentally left in from the beta?