For deffending repairing damaged structures (50% health and down) could take 10- 30x longer unless you use materials that would ballance raiding and deffending as once the structure was damaged enough it would not be repairable mid deffence unless you had materials to use up
For raiding there should be two types of guns one that damages things already low and the other that only damages full hp structures it would force you to take multiple hard to get items if you want to raid the most efficient and fast way possible the damage could dropoff and pickup for each of those raiding weapon types as the health approaches the % that the gun stops / starts working perhaps to a 80% damage falloff this along with weapon durabillity could mean you deal only 10% of the damage if you use a broken raiding weapon of the wrong type.