I can't comment terribly much on last, I never really had a "good fight" on it. I would say the wall/shutter to the left as you leave last is a bit interesting, we had a few guys try and jump over it (unsuccessfully), but you can shoot over it - maybe make it more obvious you can't jump over it, and probably put skybox down to it to prevent spam over it.
The biggest things that I noticed was the way the flank routes to mid were - pushing 2nd-mid, the one on the left goes from a building into a little cave that puts you VERY far into mid - this could potentially work, though might lead to people wrapping a bunch. That said, as someone who's made a map with a cave - unless the cave is pretty huge, people aren't going to like it. It doesn't give the flank anywhere to fight, and you can get splashed out pretty easily.
The other flank that goes from underneath 2nd onto the shutter into mid- well, it's a big ramp up that gives all the advantage to the team pushing from mid to 2nd. I suppose it might be balanced in that they then have no advantage on mid, but overall I don't know if it's the best design choice.
The 2nd was interesting, as was the mid. I liked the main structure on mid, though some of the ways the displacements interacted with it and the ramps were frustrating to walk over as you got stuck sometimes.
Wish I had more gameplay feedback, but I also had only one round on it.