Why not add some Hyperions to your fleet, they are really expensive but the speed and firepower lets them take on almost any cruiser, having a pair of them attack an isolated Capitol or just harassing one leaves the rest of your fleet time to dispatch cruisers and capitols. not the best at hunting down frigates or destroyers, but slower ships tend to get flanked and destroyed quite quickly.
I like having a fleet of them as backup on my main system 9 Hyperions can cause some mayhem. Standard weapons composition and Auxiliary Thrusters, Heavy Armor and (...umm) Hardened Systems (I think its called, for extended combat as it adds 60 sec) as built in and Extended Missiles paired with the other missiles upgrade makes them really deadly, and tanky while their size and ability to jump in and out makes them hard to destroy.
Negative traits are that they cannot stay in combat long and after they run out of missiles they are a bit weak against capitols. best tactic is probably to use them as harassment, zooming in, hitting hard and zooming out.
Gawd i love that ship.