I’ve been listening to this for quite a while, and every time I come back to this I get the same amount of enjoyment as the first listen. Not many pieces can do that for you. What really does it for me is the section a minute into the piece, and I think perhaps for you as well, because that is when the choir is noticeable. I like the fact that you have some development up to that point. Everyone has their own opinion about mixing and there isn’t one way of doing things. Really it is up to your own ears and what you’re aiming for. When I listen to music, does it move me in some way. If not, then the question would be, could the mixing fix that?
When the Stones released their last album, people were saying how “loud” and awesome it sounded. After a while though, your ears would start to fatigue, and you just had to turn it off. There is a reason why the great classical recordings don’t sound as “loud” as your pop/rock music does on the radio—dynamics. If you seek to please both worlds, you need to find balance. And this isn’t just my own opinion. I think you did just fine here as I’d actually prefer to simply raise the volume up as opposed to having to lower it. Percussion wasn’t distinct as it played more of a background role. Good! The percussion isn’t what’s important here. I like that the horns are not overbearing. It blends well with the strings. I can’t find anything that stuck out to me where I immediately thought “mixing,” and if all I thought about was the music, then your mixing is fine.
It’s difficult to mix/master anything by yourself, as the point is to have multiple ears working on it.
Overall, love the composition and your choices in your arrangement. Don’t worry yourself by putting too much weight on the mixing as that will come in time.
“A piece of music is an experience to be taken by itself.”
B.F. Skinner