All of this is sort of a half-assed, first impressions analysis. Take it at face value, I guess.
http://i.imgur.com/YPKstcf.png
http://i.imgur.com/Fnvflzj.png
http://i.imgur.com/clvqplp.png
Just about every exit from last is a fairly cramped pathway, and is also somewhat far away from the point. Combine this with the low ceiling and it feels unsafe to approach any of these exits. They don't accommodate multiple people pushing through or teammates coming to provide backup.
http://i.imgur.com/3R4ngBa.jpg
http://i.imgur.com/FJs5EXY.png
http://i.imgur.com/sPtzd6D.jpg
For most of the entrances into lobby also end up being chokes, as an attackers options are usually only to push forward or to hold back. If you look at good 5cp maps, they usually allow for a lot of lateral movement in lobby. It gives players more options in how to approach a fight.
http://i.imgur.com/sPrRXOM.png
I feel like the layout of lobby is more complex than it needs to be. For example, you could merge these two doors into one without impacting the layout too greatly.
http://i.imgur.com/35AjEiR.jpg
This area seems like it's supposed to be the main route to attack last (because of the pickups), and it could be. Problem is, getting to this area leads you through doorways that are only about one or two player widths across. The visual language of this area makes it feel like it's supposed to be a flank.
http://i.imgur.com/IFZBf1i.png
This particular room sucks as a defender, because I have no idea what's on the other side. Poking my head in is risky, and someone powerful could jump through at any moment.
http://i.imgur.com/6riKhzC.jpg
This overhang is just kinda weird. All it really does is prevent people from jumping between the spawn exit and the upper area (and demo spam, I suppose). On a related note, I'd raise the ceiling a bit - it's possible to explosive jump around the area, but it doesn't feel like you're supposed to.
http://i.imgur.com/1k4IZZS.png
There's no sneaky way to approach this door on defense's side. It's probably the best way to get shots out at people on the point, but there's such a length behind the window that offense will see you coming and have time to prepare.
http://i.imgur.com/HB0mrKj.jpg
I would personally raise this door 64-128 units. It's at a fairly significant height disadvantage to 2nd. Alternatively, I would provide another route that gives defense a better vantage point on 2nd, because as it stands, offense has nothing to be wary of.
http://i.imgur.com/2T9lWL1.png
You really seem to like doorways! This one in the middle really isn't needed at all. There's a few other instances where I don't think doorways aren't necessary, but I'll let you determine that for yourself.
All of this aside, I'm enjoying the map. It's going to need more drastic layout changes than you've done between a1 and a2, although I understand that you did those changes between two tests, so it's understandably not changed very much. Good luck!