I noticed that if you do the quest for Many-As-One and tell him that the Silent King is indeed dead, nothing else comes from it, unlike the all-out mayhem that comes from telling the Ghoul Queen. Granted, this could be explained by the hive rats waiting for an opportune time to attack, but it still seems like an oversight. I don't think this would require any dialogue scripting, just the Dead Nations being in a certain state the next time you enter it or after a certain amount of time passes (either already conquered or with the battle between the undead and the cranium rats commencing just as you enter). Though I imagine implementing this would be quite difficult.
And I could be mistaken, but I don't think Vhailor has any reaction when you start attacking random human NPC's. Seems like a very big missed opportunity to not have him turn aggro on you.