How about this:
When a city falls from realm control whilst there are rogue troops present, have a possibility that it will turn into a citadel of the undead. It will be harder to regain it, as the undead would even use the walls of the city (but would not repair them). The city would also then become a hotspot for spawning. Though perhaps the undead from the city would generally not wander all that far from their home. Maybe the same for the towns.
A better twist on this, imo, would be for rogue regions to spawn peasant militias and even recruit rogue militias from their RCs, when available, to help defend the region from conquerors. When in sufficient numbers (their cost to maintain is greater than their potential production), they send rogue troops out to neighboring lands. Basically, monster code with human rogue troops.
My point was that Dwilight had wars and massive monster hordes at the same time. There's no reason to suggest slightly higher rogue spawns will bring wars on other islands to a grinding halt.
Let's not forget here that rogue spawns were NOT uniform. Realms like Springdale had really few, whereas realms like D'Hara and Terran had a tonload. Realms like Terran and D'Hara also do not have a history of initiating any conflicts, and were peaceful realms for most of their history. For years, it really was PvE.
I'm not saying that rogue spawns are bad... but let's not overgeneralize here with simplistic comments like "when there were lots of rogues, there were lots of wars". Because there weren't lots of rogues everywhere, and there weren't lots of war everywhere either.