It depends on what phase of the game you're in, but from my current playthrough this is probably the most effective setup lategame:
* MK3 gravity turrets so you can afford to use a MK3 military station
* All forcefields you can muster to attract fire, and if necessary, micro them on and off to push all enemy ships back to the wormhole
* Any and everything else you can gather to distract carrier fire
The goal is just to keep at the wormhole for long as possible, but eventually they will get through if there's too many of them and you cannot replenish your distraction. Spire fleet helps a lot (and the great majority of firepower), and pausing to do micro and reconstruction is necessary. Honestly it does seem they are by far more threatening than any other unit because they have such gargantuan amounts of HP-per-unit-inside. Also remember to focus munition boosting guardians because they affect carriers, and flag starships if their numbers are low.
A setup like this has been working for me ever since I was beginning to get hit by ten+ carriers in the midgame; with a large spire fleet, it can continue to hold against ~80 carriers (and massive golem/botnet/spirecraft/spire waves, sometimes simultaneously), but mostly because of the friendly neinzuls spawning thousands of absorbing ships.https://i.imgur.com/pR0yW9W.jpg