Destroyers are tough McNeo, in my outcast destroyer I can take down bombers, fighters, other cruisers, gunboats, and i can severely hurt a battleship with my guns. There is no such thing as the destroyer being underpowered. And I flew a Ku Destroyer for the longest time, I never had trouble scoring a kill.
1 mortar
2 infernos
2 Battle Razors
Use the mortar with both weapons groupes, and the rest of your guns