I was about to say that the opening needed to be longer (that very very beginning), but then I looked at the artistic context and it fits perfectly.
I think if you added a bass line it could interfere with the story being told and might make it ominous sounding. If you do want to add bass instrumentation, I'd say to use strings over a pad, but that's up to you and if you want to add bass to the EQ, I'd prefer it if you simply pumped up the bass on the resonant ambiance.
The song isn't negative in any way when it comes to notation and orchestration. That being said, I don't see how the song is 'repetitive' in the sense that there needs to be more variation. I'd say it's fine the way it is.
I do think the strings <em>maybe</em> should be placed further on the outskirts of the pan to give it more depth. I am worried about throwing <em>other things</em> out there, because I wouldn't want to ruin this nice cricket sound in the pan (that's just me, though). It might be a good idea to explore the possibilities of moving other instruments out there, though. If you can put other things out there, I think the strings might be fine where they are.
At 1:44 you have this synth come in that has too much low-mids/mids (not sure which at the moment) in the EQ. It's a little jarring, but that could be the sound you're going for, idk.
The percussive, bassy synth you use liberally during the Ritual (to good effect) is a little overpowering at that point. This may just be due to everything being squished in the center pan at that part.
The cricket sample really does a good job of filling out the song.
Just got an idea that you could use a bass drum if you felt like it. I believe that would work. Doesn't necessarily have to be a kick bass drum, but could be a really low drum.
You could play with velocities and volume sequencing a little more, but that's not necessary.
Cello solo would sound great in here :)
To sum it up, it's a fantastic song that I only have a couple little problems with. Well done!