Your misstaken, its not bad mapdesign. Its designed for 5vs5 and 8vs8 games.
Then why is it in a game that's designed for 32/64-player playercounts? It makes no sense to include one map for that sort of player count when a bunch of others support the max/middle player counts. If Metro really is meant to be played at that small of a player-count then all servers, even DICE's own should throw it out the window from their 32/64-player servers.
That's ignoring that 2-3 supports can prone at different areas and pretty much lock down the areas up to the upper-floor of the Metro/third set and the "hallways" that the first->second set has/"poor map design" issues. I can bipod on a train car to the right (defending side) of A and look down the "left" (attack) mortar hole AND the middle door easily while nailing people with 0 recoil from the bipod LMG in addition to the suppression buff perk throwing suppression shade their way.