Hmmmm.
Why was Mors so desperate, if they had so many territories? What time bomb was ticking? They had a steady source of food from greenskins, and also they had a fuckton of ammo.
I think that I know: Eshin had murdered all their breeders, and they were actively losing ratpower. That's why there are no slaves. They were all promoted to clan rats, because there was way too much equipment for so few rats.
Think about it. Only clans with excess population can afford to throw skaven lives away. What if they aren't getting more slaves? What if they can't even get more Skaven?