As it's been said, carriers are the key to easily win, even in hard.
Bolter drones will easily destroy small ships and can even handle larger ships with manual targetting. So you should buy them right from the start.
They are also useful at taking out missiles, which are the biggest threat in the game currently, as they ignore shields.
For taking out larger ships, I found out the best is to only equip nukes. (which I think are currently overpowered)
Nukes do 400 damage to hull and 800 damage to shields, have an almost unlimited range, and travel quite quickly. They are expensive (1800 scrap each), but once you aquired one, you won't need to put upgrades in it (as they can't be upgraded anyway), so you can focus on maxing out your number of drones.
So at the end of the day, smaller ships and enemy missiles will be dealt by your drones, and larger ships will be instantly blown by 3 or 4 rockets.
I easily finished hard mode with the Valhalla (Heavy Destroyer Carrier), and 2 Revolutions (Heavy Assault Carrier). With 4 sets of Bolter drones, 1 set of repair drones, 1 set of shield drones (which weren't even needed) and 7 Nukes slots.
You can even warp right into a group of large ships and watch them blow 1 second later.
