The greatest problem why frigates of Combat/Technology specialists can solo fleets is most if not all pirate and Hegemony ships have regular crew, which means they do not lead their shots very well. I can circle-strafe the rear of cruisers and Onslaughts, much like it is done in early FPS games like Doom. Onslaughts fire at my ship, but they usually miss as I just glide to the side and rake them with heavy blaster spam. If Hegemony had some ships with elite crew plus some levels of Gunnery Implants, such that it can lead shots effectively, it could make twitch-fighting much harder.
If the player is not good at twitch-fighting, low-tech or midline ships are better since they can mount needlers and maulers then snipe and kite. High-tech ships (except Omen) are great at burst damage and mobility, and if they can dodge incoming shots, they can smash ships quickly. Heavy blaster is great - it is a medium weapon with the power of a large weapon. Its only weaknesses are short range and high flux costs, but if the player can mitigate those, his high-tech ships will be DPS monsters.
Xenoargh, the first time I tried a double blaster Tempest against a defense fleet, I disabled several ships and severely damaged an Onslaught so quickly that it admitted defeat. I harried the rest of the fleet, then they decided to turn around to fight another round. I have not been able to reproduce this anomaly. I probably could have soloed the entire encounter with one Tempest.