Yep, War spoils is useful for

1) Attacking when you're unbreakable already
2) When you can beat everyone back (i.e. all enemy attackers attack out on a single wave, you attack out next tick as an Avian or tact or high rax to get land in and army back out before they all return home
3) Attacking in peace time, especially against an enemy that could ambush you but not trad you back.

and most importantly

4) Trolling teammates as a Faery.