I nominate: Steppe Castle 2, Ulbas Castle, Phoenix Castle, for removal or tweaking.
Steppe Castle 2 needs another way to flag outside of a thin stairway that is incredibly easy to defend and fall off of. Ways into the castle are fine, ramp, backdoor, gate, but ways to the flag are... well, one, outside of ladders. A good map should have at least two entrances to castle and flag area, IMO.
Ulbas Castle has a similar issue. Only one vanilla way into castle. Needs a back entrance, preferably large, breakable doors in place of the large door-like textures.
Phoenix Castle has plenty of entrances, but they all take very long for the attackers to get to. Attacker spawns need to be modified, badly, as often attackers will get stuck in a pit as a spawn.