Hello! I don't think I've seen you around here before. Have you introduced yourself in the intro thread? If you haven't, you should.
You've got a start here. The one thing I think could stand the most improvement is how bare it is. The entire thing is made up of legato strings going from chord to chord. Don't get me wrong, there's a time and place for that sort of thing, but it can get old pretty quickly. As it is now, I would call this closer to ambient than orchestral, even though it uses string samples. Strings are capable of so much more than simple legato. Why not take advantage of that?
Some context might also help. Is this supposed to be a soundtrack or a song in its own right? The demands are different depending on the answer. If this is just supposed to be played behind dialogue or as ambiance then generally you want to make it less distracting for the listener.
You have some dynamics in place already, which is good. But see if you can't add some more. Really push more emotion out of it! Check this out if you need an example of how emotional strings alone can be.
Also, you might want to think about amending your chord progression. My ear training isn't what it used to be, but it sounds pretty basic. Try adding some secondary dominants or subdominants. Really crunchy diminished seventh chords might also be good because the subject matter is apparently supposed to be dark. And don't be afraid to experiment! There are many other types of chords as well. See what sounds best to you. It also doesn't seem like you modulate either. For a track this long you may want to modulate, especially when (like with this) the articulations aren't varied.
I just thought I would add that the string samples you use are not that great, but a lot of people can't afford better ones so it's not necessarily that important.
I hope that helps!