So I got a game on this a while back, sorry it took a while to get you some feedback, but better late than never! First off, I just want to say that the map is very easy on the eyes, something that's hard to accomplish with the Erosion pallet. The level of detail was great, major props there. However, I did notice a few issues with the layout of the map, weapon choice, etc.
The first thing I noticed was the placement of initial spawns. Red team spawns considerably higher up than blue, giving them and advantage right off the bat. Also, red team is basically guaranteed the sword since it spawns much closer to them than it does blue. Which brings me to my next point - the sword. With smaller team sizes, the sword generally isn't the best weapon choice because it takes very little skill to use. And this is especially so when playing on a cramped, CQC-style map.
Now onto the actual map layout. Decay almost felt like two different maps squished together. The bottom portion of the map was very cramped and linear. There just wasn't much space to move around in those lower rooms. And by linear, I mean that there weren't many movement options between the rooms. Basically, once you get down to the bottom portion of the map, you are forced to either keep travelling in one direction until you get back up to the top portion of the map, or turn around and go back from where you came. I'd like to see more interaction between these rooms and the top half of the map.
Now the top area, instead of being too cramped, felt just a little on the open side. It's not as big of a deal as the bottom being to cramped/linear, though. If you can find some way to create more connections between the bottom and top halves of the map, that feeling of "too much open space" should be taken care of.
Hopefully that helped some! If you have any questions feel free to let me know.