Yeah you're right. I'm going to expand the lobby quite a bit and add another entrance and probably a second floor. Will also redesign the last point somewhat. Got tons of ideas from tonight, so thanks.
I agree with everyone else who said the overall scaling is a bit high, at least in the size of the area around the first capture point.
EDIT: one other thing I think would be good would be to have more nooks and crannies to duck into as a spy in some of the open areas. Some of the hallways around the last point felt too tight to maneuver comfortably as well.
Metal around A : move the existing stacks to more obvious spots (especially that big box), add one or two additional medium boxes between the point and BLU's spawn. General area around A could be a little overscaled / too open.
B was alright with me in terms of layout and scaling, but I think BLU's spawn times are too long. For A/D maps Valve's spawn times are 2s for BLU and 10s (default) for RED, and I think you're a little far from that. The final room could be a little biger as was mentioned (plus big, impressive final rooms give a sense of grandeur to your spytech base), but make sure that there are at least one or two sentry spots that can cover the capture area and can't be easily outranged from anywhere the attackers are coming, the wrangler shouldn't be a requirement.
For the next version I've added a forward spawn for blu... I've also fixed the spawn times (accidentally had -2 for red on the A cap, rather than +2). I'm also going to look into redesigning the B point, or at least expanding it quite a bit. There's no real place for blu to set up a forward base at the moment, so I'll try and work on that.