The blend of instruments is great, the whole thing flows well. I can't really hear the 3 melodies, but I do hear a great "sound-scape". You might want to try making them a bit more pronounced, and maybe add a break in the song (try using supersaws for the really top melodies, they always get heard over everything).
If you want a boss battle, you normally have to stress people a bit more, and make them feel scared. Here are two examples of what I mean:
You couldn't sit still and do something relaxing with these going in the background. Your song is missing that hyper-agressive beat that would make it a boss fight, imo.
Still, good work. Although I wouldn't see a boss fight here, it still is a good reflective mood music. Keep it up!