There are 2 vital spawners which are currently not working.
Skaven elites cannot spawn from wall holes, ground holes or climb-downs (like the pillars in the finale of Righteous Stand). This affects a lot of maps, as most maps use this type of Skaven spawner.
Lord spawners (for the adds in Lord events) are broken on Into the Nest and Warcamp. This means there will be no additional spawns in those boss fights, even on Cataclysm.