Just finished my playthrough, and here are my thoughts:
Spoiler below!
Atmosphere: 4/10. Not trying to be mean, but hear me out. I saw many, many, many lights shining through walls, flickering textures, areas with no ceiling, etc. and it can very quickly ruin the immersion of the player.
Story: 6/10. Again, not trying to be mean, but I truly don't know what my overall goal is. Why did I kill Herr? Why did I fall through the water and end up in some secondary realm? I think there need to be more connections between the gameplay events so the player has a sense of direction.
Level Design: In some areas, 4/10. In others, 9/10. The area I most enjoyed was the realm of reflections or whatever it is called because it was a very unique area. Going through different doors activated different things in the same room, and the player has to solve an overarching puzzle through using the different "powers". Other places, however, just didn't feel all that impressive, particularly the library. It just felt like several rows of bookshelves that would never have been placed that way in real life, and that was really all there was to it. I think going into greater detail to make unique areas (like the world of reflections) would serve you well if you did it all over rather than in just the one area.
Gameplay: 5/10. The monsters were unpredictable, yes, but a lot of times they didn't really make much sense either. For example, why is this grunt that has been walking in front of me the whole time now spawning behind me? Why is the brute on the other side of the breakable wall when there is no way for it to get in or out otherwise? Being unpredictable is good, but making no sense is not. Try to find a balance between the two. One doesn't just disappear randomly, there has to be somewhere for it to GO so it can pop back up again. Even if there are supposedly multiple monsters, having it disappear at a dead end makes no sense to the player.
Puzzles: 7/10. Not too many of the typical "use key on door" things, and a lot of puzzles were quite unique, particularly the entire world of reflections. However, that was really the only puzzle that stood out in my mind, as the rest were simply fetch-and-use puzzles which, although they weren't always keys, they did tend to work like keys. I think if you mixed things up a bit, you could accomplish a lot.
Overall: 6/10. There is still a lot of work to be done. However, you have done a good job so far in many areas, and other areas just need a bit of improvement. I hope you will finish this story, because I think it is definitely worth it.