Think it would need the Extended Cut DLC as well, but yes I think it would have improved the ending. My problem was the lack of forshadowing and the fact that it was so fragmented.
Leviathan provided a component I felt was missing, the mystery to follow and uncover. I still don't "like" the ending, but I'm fine with it now that I see it in the context of the Extended Cut and Leviathan.
That said, I kinda wish I could play the game like Brad did.
I only have one gripe, sadly it's just really big.
I just don't like the suspicion stuff for your disguise. I much preferred how it worked in Blood Money where you were in disguise as long as you're not entering forbidden areas and so on.
One can argue that it works better since it was weird that a bald man could stand next to a security guard while wearing a guard uniform. On the other hand I find the whole "use instinct to rub my bald head to reset people's suspicion" to be even worse.
At least it felt more that I could focus on the puzzles with working the level when I had the guarantee that my disguise would work as long as I didn't act weird.