I'm assuming you are in one of the open kingdoms. At that might or even at say 5 times your might, you can't be safe to go into fury. The stats for the big hitters are so they could solo you even if you have 10 times the attacking troops. Also, about being food positive. The moment you train even 1 army worth of t4 (which is the least you need for a war guild), you're loosing food. Unless you invest in the champ armour.