NT's writers arent't the ones who wrote any of their games. They hired writers for HS and Enslaved. So for all their great story telling reputation they haven't actually writen any of their own games till now.
Then who's writing the story for DmC?
As for the Unreal Engine? You think that if Capcom didn't want to they couldn't have access to it? MTFramework is a great engine, even if Capcom hasn't been using it to it's full potential recently. Besides I've seen DmC in action, the graphics aren't so outstanding that they'd make or brake sales.
They could use UE, but because fans will constantly complain about UE3 not being "fast enough" for DMC, I doubt they would. I'd say the graphics, true, aren't ground breaking, but I gotta say, they do look better then DMC4's graphics, but that's only cause DMC4 was back in 2007. Even so, the graphics and detail in DmC is pretty deep.
As for the story? i still don't think DmC is that great an improvement over the original franchise, they just went from what's tacky in the east to what's tacky in the west.