i don't use defences at all on my main base. they just hinder my movement. and every time i hear "ground is shaking" i just run away from my home and shoot them all (they always prio killing me instead of damaging my buildings if nothing prevents to reach me (though if they attack from the side of a boar\wolf farm ... i just sigh and ship a new bunch of enemies after attack. cuz troll's aoe usually deadly)