Sounds like that harp may be mic'ed a bit too close. Also noticing a lot of instruments seem to attack at exactly the same millisecond when multiple notes are played -- humanize those ms.
Dynamics of the piece are already very pleasing by 0:33.
I can't tell if that's a koto or shamisen for not ever having studied the difference much, but particularly nice job with them. They sound very organic.
I could do with a bit less reverb on your bass.
Synth at 0:46 that sounds kind of auto-filtered could also come down a lot. There's nothing in that frequency range, so it ends up sounding hugely loud by comparison -- at least to someone my age who hasn't lost that 19k-24k hearing range.
1:50, I think the reverb/low end gets a bit out of control, starting to overwhelm your leads a bit. This presents a bit throughout. I think it's mostly reverb. I'm hearing a lot of low rumble, not an organic breath from either low organs or strings.
Vocals are very clean and of course distinct. I'm pleased they don't dominate the track and are tastefully interspersed throughout.
Compositionally, this is quite a journey, though I notice a relative lack of overarching melody.
2:04 to 2:07 chord modulation was unexpected and quite pleasing, as is the following development from 2:20-2:27. I'm wondering just how far you will push us before driving off the cliff -- and am disappointed somewhat not to have had a fortissimo swell anywhere.
3:06 sounds great.
4:07 to the finish line impressed me enough I didn't really mind the slightly high reverb wet signal, which of course, as you know, is every cinematic/orchestral composer's favorite cheat plugin.
Overall, awesome work. I think I've said most of what I could possibly say aside from that.
Quick note, are you sure it's your workstation struggling with the project load, or your computer? I used to think my DAW sucked until my actual computer started failing. Subsequent upgrade fixed all the problems I was having. For your sake, I really hope it isn't computer failure.
Thanks for coming out to NGUAC!