Well, in my opinion main problem with Gravel Pit is the map being unbalanced. While A & B are extremely closed, C is extremely open. A is far away from both spawns, and B is close to both spawns. A is easy to capture when BLU team gets an advantage, and usually don't worth defending when they start capping it. B, on the other hand, is even more closed than A, and because of this often ends as a turtling spot and choke point. C is very open and caps very fast and a single stickyjumping Demoman, rocketjumping Soldier or a Scout sneaking in can win the game.
I've tried to kinda reverse that, by making A & B open, and C closed, thus hard to break in, but when accomplished, the result is overall victory. Of course, some cover is always needed, but a) not too much b) map is still in development. So, that's my point of view. Of course thanks for any feedback that I've gotten and that I'll got in the future.