Apologies for drawing over a10, but I'm guessing it'll still be useful to you:
Here are your main issues:
Not a single building effectively cuts vis because your buildings are all empty boxes with a window or a door on every single side, so a line of sight can be drawn from one side to the other without even trying.
Pretty much every single building is just an empty box. Four walls, some windows, some stairs, and that's it. No internal walls or anything. It's pretty terrible.
Even ignoring your building problems, the red lines are sightlines around the buildings themselves. You can see everything, from everywhere. The glowing building would be fantastic for splitting up that 90 degree corner, except it's a seive, so you may as well func_detail the whole thing and forget about optimisation.
Here are some solutions:
As you might have guessed, I think you should put internal walls in, take out windows you can't shoot through so that you can't always see from one side to the other with your buildings. The glowing building is the most important here. You need to make sure that you
absolutely cannot possibly see from one side to the other. You can do this with internal walls, closing up
all of those massive, functionless windows and making sure the doors can't possibly see each other around the internal walls.
Once you've done that, put a sky brush along the top like I've done here in blue. I'd advise making the building taller too, this is your main vis blocking building, it should be tall.
Next up is increasing the height of all of the buildings I've put sky brushes over and adding the sky brushes as I have. The one with the barrels I've extended to be in line with the corner building's sky brush so you can put a hint between them (the green brushes). I've splinked the hint brushes between corners of buildings and flush with walls where I think it'll help you, but you have to do the supporting work blocking vis through the buildings to help.
I have angled the latter section, I don't expect you to do this, but you ought to be moving that stuff back around so that your angle is less 90 degrees and more like 110 or more. The fact that you can stand on CP 1 and snipe cp2 is fucking ludicrous and you NEEEEEEDDDDD to section that shit off. Always try and build arenas with divisions. Me and frozen fucked this up with snowplow and have been trying to sort it out since. Dustbowl is the perfect example of this. Every CP is in it's own arena with a big division between them. You don't have to go
anywhere near as extreme as dustbowl did, but it illustrates the point well.
While writing all this I downloaded 11b and looked at that and you still have some really fundamental issues. Everything mentioned above is still there.
Your visleaves are something like 2000 units tall, which is reaaaaallly bad, especially with short buildings. here's a diagram taken from this
excellent article that you need to read (if you have already done so, do it again so that it actually sinks in):
Without the hint there, the visleaves around the engie and the sg would extend upwards to the sky, since you can move up to the sky above you without leaving your visleaf, and that would allow you to see the SG,
you can see the SG from the ground. You have to cut the visleav so that the one you're in, can't get into a position to see the SG. So you need to take a huuuuuuge hintbrush that covers the whole map and put it 128 units above the ground (use cp1's ground). Then put another 256 units above that, and another 256 units above that. The first one will stop players on the ground seeing over buildings, the other two will help anyone jumping from seeing too much.
Moving on to the next issue:
You need to cut shit like this out. This is horrible. (I'll ignore the fact you don't nodraw the tops of those brushes and so have wasted lightmap data)
Buildings need their tops. If you absolutely must have a sloped ceiling as well as a sloped roof, add that separately so that it's a worldbrush and flush with the tops of the walls. Better yet: add a floor above what is accessable to players and have your roof much higher up. Then only func_detail the
actual roof. Don't leave your buildings open topped until you actually understand vvis and understand when leaving an open topped building isn't going to cause problems.
Using r_drawfuncdetail 0 shows the problem you have with windows.
Standing in this doorway near cp2, what is that poster I can see?
Oh. :|