So much is dependent upon your archery, military tradition and logistics levels but here is a basic guideline that should give you no losses when farming NPC's. As your research level's increase, you can play with these numbers and see what works best for you.
LEVEL 1 NPC: 50 ballista and 50 transports
LEVEL 2 NPC: 80 ballista and 80 transports
LEVEL 3 NPC: 165 ballista and 165 transports
LEVEL 4 NPC: 275 ballista and 275 transports
LEVEL 5 NPC: 500 ballista and 500 transports
* The lower your logistics level, the more transports you will need.
Subject: Npc Farming with Ballista 
Sat Dec 05, 2009 4:47 am
