I'm having issues here trying to suggest a direction for you to take...
One side of me feels that the song is incomplete and agrees with the person below that it needs some more variation. Buuuuuut, at the same time... it almost feels like if this song had vocals on top of it, it would already be complete. It feels ripe for some vocals w/ fx. Almost Nine Inch Nails crossed w/ Daft Punk Vox or something. In this sense, every element of the song would be tied together and it would feel awesomely complete. Even a vocoder w/ FX would do.
You have got a decent structure set out for a vocal version. The only thing I could really suggest is adding some sort of bridge to break up the continues music. You do that towards the end before the last "chorus" but I think if it were longer and had more of a build into the final chorus it would feel more complete. The mixing sounds good, nothing special though. As a final mix, you may want to bring out the kick more or bass. Accentuating portions of the song so that the listener is really drawn in (Hurray EQ cuts!).
So with all that being said, the instrumental is pretty good by itself, it's just a little repetitive. So the way to solve this without adding vocals would be to add some sort of lead that basically does the same function as vocals. This lead should not be repetitive and even each chorus it should be slightly different. You want the parts to reflect the same feeling but in a different way. An almost flute-like lead here (well sorta - you already have one) would be epic. That or some sine-wave type lead. Maybe a badass distorted lead would fit, but it could overpower. I'd say experiment with sounds til you find something you really, really like. But remember that you really have to vary it throughout the song so it feels to the listener like it's going somewhere. I find the best way to do that is to find your synth patch or sound and once you have it, put the song on loop and just play around with ideas on your keyboard as it plays. After awhile, you'll get something you like and it'll develop.
So all in all, epic song for me to keep on loop like it has been last ten minutes :D - Also, this gave me the same feeling that Matrix song (red dress girl one) did when I listened to it :D