Very difficult to attack. Being on the losing team throughout the entire playtime wasn't really fun because I don't think I saw the cp captured by my team even once.
Possible causes :
The access routes are few, and too convoluted. Basically there are 2 routes that are somewht direct, the catwalks on the right. The vent 'pipe' is pretty gimmicky. Accessing the catwalk on the left is a very long walk (despite the surrounding building being your team's color, the other team can reach it much faster). This means the players on the control point have mostly one direction to watch.
-> Try to shorten the paths to the control point where possible. Your ramps aren't steep enough, most of them are on a 1:2 ratio, sometimes less, make them 2:3. Promote attacking from the left side more by shortening that path.
Then, the entrances into the middle area are very narrow, while mid is relatively open in comparison. This means that if you're trying to get into mid, you can receive spam from many directions through your chokepoint doorway, but you can't spam back. The catwalks themselves are pretty narrow. Spawn exits are also narrow.
-> Widen doorways and catwalks where possible
All of this combined means that once the other team has taken root on the point, they are hard to dislodge, you will die when moving in, and when you respawn, you will have to walk a lot, before dying again.
-> Try changing the respawn times after capture to something closer to an A/D map than viaduct (ie 3/9 or even 2/10 instead of 4/8)
EDIT : one more thing : the bottom part of your ground brush still exists in the bsp. Looks like you have some sort of empty space here : remove the skybox brush on the bottom of the map ?