I got jumped in the early game by the Dregin AND the Yor... and, out of desperation, I sort of stumbled on an idea (I'm sure has been tried before): Sniper-class warships.

Essentially I use a cargo-class ship, put one (and only one) of my smallest weapons on it, then with the remaining space I use about 50% of it for engines, 25% for sensors, and 25% life support (space- and need-depending, of course). I call it a Sniper and it's great for hovering around the edges of an enemy empire, swooping in and killing undefended starbases, constructors, freighters, and troop transports (even right next to enemy planets with warships in orbit), then escaping well out away from the enemy fighters-- all in one turn! And when the enemy sends a fleet of fighters after your Sniper, all the better because you can lead them on wild goose chases.

Even now that I have medium size hulls, I'm still building (much upgraded) Sniper-class ships. I couldn't imagine waging a war without them!

Of course you've got to "fly" these Sniper ships pretty carefully because if they end up within firing range of enemy craft they're sitting ducks, so good sensor range is a must, and some very micro-managed flight paths. But if you want to punish and torment the AI, the Sniper-class warship is great fun!

Of course, don't forget to check every target first and make sure it's not a SB with defenses, or the icon of a transport but actually a small fleet with a transport protector. Spying is your friend.

Enjoy.