Id like to also add that with Phase Stabilizers, you are nearly impervious to a flank attack.
Building smaller fleets at star systems or one or two larger fleets to defend the main system works great, they can either stomp any attempt to break into a planet, or hold off a larger fleet until you can recall back (hopefully you can do it nearly immediately with your Marauder level 6 ability). You may still need strike-craft defenses, or in very hot zones, static turrets and other tactical structures, but your fleet can be right there too in the thick of it.
Enforcers and Skirimshers get a powerful heal ability, but in order to use it effectively it needs to be micromanaged in combat. Usually on small scale combat, it isnt used that often because concentrated fire will wipe out anything before it can heal. But on larger scale battles or very small scale combat, micromanaging Reintigration can save ships, resouces, and planets & structures against would-be assaults.
Also a lot of techs and abilities revolve around speed. Speed of fleet movement, jump-speed, speed in enemy detection, speed in kills. So keep that in mind, you want to be where they dont think you will be, and be able to retreat faster than they can catch you. With our last phase-space detection tech, our intel is teriffic, but you have to be vigilant or it will be for naught. With that information and Phase Stabilizers, you can be prepared for nearly anything at a moments notice, offensively or defensively.