I'm fairly new to the game, i've been mostly using autofits and designes from the internet so far, without really knowing what i was doing. Then a few days ago i went on a deep dive trough the online tutuorials and actually learned about ship design.
Naturally there is a lot there and i don't think i did more than scratch the surface just yet, but there are a few sort of unwritten principles that nobody seems to talk about, but following them i was able to design a couple ships myself that performed really well in sim.
First and most important one is, flux vents are more important than weapons. I think it's a very common newb trap to feel like you need to put something in every single weapon slot. I know i felt like i had to do it at first too.
Big mistake. 2 weapons that work are better than 6 that flux out in 5 seconds. Adding flux vents is a bit of an art but in most cases more is better, which is the opposite of true for weapons. You add weapons to perform speciffic roles.
Second, hull mods can really make a difference. It's almost always beneficial to have the range advantage over your enemy, if you can fire at them where they can't fire at you you can flux them out with little to no danger to yourself, while their ship hopelessly tries to keep up with you. On the opposite end, safety overrides on a frigate. You might say a frigate is already really fast, why make it even faster? Well, that's the point, add safety overrides to something that's already fast and it'll be zooming across the battlefield like a crazy and very *** off hornet.
Third, missiles can be a game changer. AI is generally very good at lowering their shields when they are near fluxing out, but toss a few sabots at them and you may very well flux them out and then they are a sitting duck. On the other hand, reapers. I've seen skilled player5s destroy massive stations with a single phase ship using reapers. Now those players did build their entire character to be able to do that but reapers really are that potent if you use them at the right moment. Rule of thumb is use reapers if you think there's a very good chance you will hit the enemy hull. A couple of reapers can punch trough armor on most cruisers and take out between 40 and 70% of the hull on top of that, not to mention that you can then unload into that hole in the armor with your guns.
Just remember missiles are limited, they are a game changer but only if you don't waste them. I've yet to learn all there is to know about missiles. The two i mentioned are the ones i have found can swing whole battles but they are by no means the only ones nor are they appropriate for every build. Also if you are giving missiles to the AI make sure they are linked and not alternating. 3 reapers on the Dominator can be absolutely devastating when fired together, but fired one at the time they are liable to be taken out by PD or absorbed by shields.
Properly outfitted fleet can dominate a mirror fleet that's not outfitted well. This is something well worth taking time to learn.,