First of all let me say I enjoy playing the new faction and the things they have added are good, however I feel that some things could be implemented to better round off this amazing new faction, I will list them here, I am aware that some of these suggestions may be difficult to implement but are worth the effort.
1. We need undead champions. It seems odd that living people would join an undead kingdom but hey, they may have a skeleton fetish, not that Im judging or anything.
2. An ability similar to the Silver Tongue ability, except that it costs mana instead of gildar to recruit "wild" undead units.(After all the undead should not be fighting each other)
3. The night of haunted dreams random even should be a boon to the undead faction, perhaps a random unit will join the undead faction as long as the cemetery remains open?
4. Perhaps the catacombs and necropolis could add 1+ "growth" to undead cities, especially useful for cities not on essence tiles, and makes sense lore wise as excavating these buildings will unearth more bodies.
5. Flooded cemeteries and other lairs that house undead monsters (minus butchermen) could count as population boosters, or mercenary camps, or maybe add a growth bonus?
As for gameplay perhaps the undead could suffer a -1 diplomatic penalty for being dead so to speak? It seems they are already reviled by the other factions.
If I think of anymore I will add them here but I feel that improving these aspects, minus the bug fixes offer the easiest route to better improve this amazing DLC.