Hmmm that's odd I've never heard that mobs could constantly respawn like that. Guess that GM was just being stupid and could have said "yes the mobs are supposed to respawn like that." Doesn't really explain though why after wiping out 1 wave fully ----> 60 minutes went by with no NPCs or mobs up with like 20 people pounding on forts ----> wave comes and retreats ----> another 30-40 minutes goes by ----> then the wave that lasted about a full hr came. If it's not broken SE needs to do something like award union drops every 30 minutes of campaign or something.