Honestly the dwarves city design seems average at best.... A big cavern with a settlement in it protected by walls.... Like everyone is saying its basically a human underground settlement. The way I see it it should be a bit like the lonely mountain in the hobbit movies. A big wall with a huge reinforced gate leading under the mountain and from there you could have a great hall, hallways, bridges, etc. leading to the victory point or whatever layout they feel like doing. They could also put some smaller barricade/checkpoint after the main wall/gate is breached if they implement (I hope so) layered city defense like they should! All in all the siege maps look very very blend right now for every races not only the dwarves.