My tactics:
1. Avoid them if possible. Don't try to fight them in the early game. Research warp drives, sensors, life support, and diplomacy to get good deals from your friends.
2. Make sure you get Eyes of the Universe (15 sensors, without having to put them on the ship). Design cargo hull with a small weapon, lots of engines and support, and start hunting undefended starbases, constructors and transports.
3. Tech trade. Someone may have obtained tech from the Dread Lords, or researched it. With high enough diplomacy, even the Yor will give you good trades while you're at war with them. The next step: cargo hulls with hyperwarp and blackhole eruptors, in fleets of four. Attack single ships and fleets of two, and they will most likely die before being able to shoot back. Make sure you're out of their range at the end of a turn. Also upgrade the single weapon cargo hulls to hyperwarp, I have them at speed 43 now, range over the whole map. For the heavier attackers, get at least 23 movement.
4. Invasion, soldiering upgrades. Get really fast transports. Use armed cargo hulls to blow up planet defenders, then invade. Shoot any troopship attempting to approach.
5. Against the nastier fleets, a fleet of three large hulls with eruptors and nano rippers, defenses if you have them (zero point armor is nice if you can obtain it). It's not essential to attack their fleets, just getting the planets is enough, but sometimes their fleets are annoying. With experience, they will get some impressive hitpoints. For attacking a large fleet (the most I've seen them use is 4 ships), I use 3 heavies plus one sacrificial cargo with eruptors. If you don't get all of them on the first attack, the cargo will absorb the first shot (and die, but at this stage you should have the economy to replace him in a few turns).
6. Some of his heavily defended starbases remain difficult to destroy. It would probably be best to ignore them as much as possible, just bypass them and get his more of his planets.
