Fair enough on the not ruling over a wasteland, but if the summoned shadows create shadow spawn when they kill say 675 commoners on the first round assaulting a city. Those shadows aren't summoned creatures and are not stopped by protection from evil, and are free to transform more victims. I see that more as rapidly multiplying problem.
In my game I am putting harsher limitations on the ability itself, such as only 1/minute and can't travel farther than 100ft from Eustoyriax himself.
Seannoss - I always assumed shadows never did that because they have no inherent leadership, and were more instinctual than anything else. The summoned shadows obey orders, which then create non-summoned shadows which attack the nearest available sources of life.