I was using Stormdrum 2, which I'm having difficulty sending the channels to the mixer board since it can only be channeled to inserts 1-12, in which the program (Hypersonic 2, which I use for the majority of the instruments I have playing in a piece) use...which are inserts 1-12. So it's either route Stormdrum 2 for mixing or Hypersonic. This is all in FL Studio, I don't know much about Siberius.
Anyway, although I do love the drums, when it comes to a cavern, I'm thinking the drums along with the rest of the instruments could stand a bit more reverb and possibly a certain delay effect. Couple this with a higher "Attack" which fades in to a note before you can really hear it. I would also say lower the volume on the drum without sacrificing it's power and sustain the reverb more to give almost an echo effect as you would hear if you yell inside of a cave.
I can hear a lot excess frequencies that can be cut out to make the instruments more clearer which can be done using a parametric equalizer. I don't know if VSTs can be imported in Siberius but in case they can, definitely look into getting one. More reverb plus excess frequencies means it can sound a bit cluttered, which I can definitely hear as I play these.
To better explain frequencies, for instance a kick drum, doesn't use a lot of treble but without a mix it will have both bass and the "excess" treble in there. So with an EQ you can cut out the treble which will make the bass sound of the drum clear.
But that is mixing...so it might be a good idea to kinda research on some mixing tips as it would make your piece sound more clear and have a fuller sound.
When it comes to live performances, in my experience, the mixing and sound design is done before the performance even starts so the band doesn't have to worry about the sound as much as keeping up the tempo as the rest of the band.
I would say I'm better at mixing than orchestration but composing is fun so I do it anyway hahaha.
It's actually whatever sound set came with Sibelius 7! I don't know much about sound engineering or mixing, but I have figured out through tinkering how to adjust some of the settings to make some of the drums sound closer to a live sound. I've done the most tinkering with Taiko drum settings, similar to the epic sound you were going for in your composition "seventh insignia."
Hahaha, yes, that's what I thought might happen!
It's more of just having something for the audience to latch onto. I was taught the concepts of "waiting time", where the residual atmosphere of the piece should leave enough space to not be absent, and "repeated time", the point where a certain figure becomes very obvious, and thus obnoxious. For phrasing, it's all about waiting time. Classical and baroque composers, for the most part, liked having things going on at all times, and didn't worry about it much. In your case, in an effort to create a relatively literal atmosphere, you added some space between lines and melodies so the background could sink in. Waiting time, however, adds up; it's not always based on one certain instance. That's why it felt a little more empty than I would have hoped.
I'll do commissions when people want them, but am trying to get my teaching certificate right now. I appreciate the comment though, I like to think my time learning music has been put to good use!