[Sombre]

I would actually increase the siege to 2 and castledef to 3 on dwarfs. Every dwarf, even a random young warrior, knows more about tunnels and structural engineering than just about anyone (barring specialists). I gave all skaven siegebonus 1 because they can all dig tunnels, but skaven tunnels are dangerous, poorly constructed things and they generally break sieges in the most volatile and crude ways (with poison wind, warpfire and collapsing huge quantities of earth, perferably on 'spent' slaves or rival clans).

Take for example karak eight peaks. There are no more than a couple thousand dwarfs in there and there are countless thousands of greenskins outside and skaven below, but they've held it and sieged/taken it back numerous times.