I tend to avoid frigates mostly because they just don't kill fast enough. Almost all fights in the game I fight when outnumbered 120 to 180, and the most reliable way to win is by having ships that can burst down enemy destroyers immediately, quickly gang up on cruisers, and then camp reinforcements. Frigates can't do that, outside of the few premium ones (SO Brawler, Tempest... and that's it I think), and even when they do, they are worse than destroyers at it (die to fighter swarms, run out of PPT).
It also somewhat boggles my mind that most frigates in the game are intended to be "support" ships that can't achieve much on their own and are supposed to escort bigger ships. What's even the point of an escort that has PPT 3 times lower than it's mothership?
My fleets usually are composed of 5 ships of each class, minimum, plus the fuel, troop, and cargo haulers. The frigates I have are usually used in hunting down fleeing enemies. Sure, my 4 tach-lance paragon can literally delete several frigates with one click of the fire button, but it is annoying to keep chasing them. So usually, if I deploy frigates, they are either deployed and ordered to be escorts, summoned as reinforcements once my big ships have worn down their big ships, to go kill and chase, or sometimes used only in the second engagement when I am pursuing the survivors.
I know people love phase ships, but for me, the Medusa destroyer is queen of the chase. I usually have an officer commanding a medusa as the head of my pursuit fleet.
Exact loadout: 2 light needleers up front. 2 Heavy Blasters, 2 IR Pulse Lasers on the front side mounts, and two burst pd lasers on the rear mounts. 1 capacitor, 19 vents, hardened shields and resistant flux conduits.
A small squad of these can burst down shields and hulls super fast.
They're not meant for long duration missions, they're meant to show up, blow something up really fast, and get out. That's how I use my destroyers, and my frigates.
Now, when running an all frigate fleet, there's something to be said for getting the damaged and worn down ships to retreat, and sending in a second, third, or even 4th swarm.