I think that Guardian Frigates don’t really work as they should. They can give the team a missile defense, and some neat debuffs on the hostiles coming too close, but that’s about it. As far as I understand, I think Guardians should be able to stand their ground for a long time. They do have better self-heals and better resists, but still I can see quite a lot of them just pop out of the sky within seconds, because ~50% of hell of a lot of damage is still hell of a lot of damage.
If I understand their concept, they should be able to survive that, they should be able to stand in the first line and take some hits for their teammates… but they can’t really do that - or in some well organized team situations an Engineer or a Command Fighter can easily do this better than them.
Furthermore Guardian Frigates are quite boring to play. They are the slowest ships in the game, they don’t get to the action in time or they often get left behind. They don’t have much attacking tools to have fun with, and compared to their size and speed, their defenses are only mediocre.
All this could be fixed with a relatively simple change, making it a more fun class to play and allowing it to really be the “tank” of the team:
Change the Phase Shield so that it doesn’t just give a flat amount of resistance boost, but instead limits the maximum damage the ship can take from a hit. There should be a flat amount, e.g.: 300 dmg (just a random number, balancing is up to you), and whatever would hit the ship for more than that will only do this amount. Also this should work as a Passive, and could be modified by the tech level of the equipped shield modifications.
Plasma Gun projectile hits Guardian for 220 dmg → does 220 dmg. (keep in mind though that this weapon can fire really fast)
Coil Mortar projectile hits Guardian for 1200 dmg → does only 300 dmg.
Nuclear explosion hits Guardian for 12k dmg → does only 300 dmg.
Imagine it as the hardened shields what Immortals in Starcraft 2 have. It protects the ship from really big hits which would decimate it too fast, but small, fast firing weapons or focused fire would still be able to bring it down relatively fast, thus Interceptors would still remain its natural counters.