[ZeroAdunn]

I once ran into a problem where I my small three system empire was attacked by a fleet of twenty ships (most of them cruiser or above)

I sent a small fleet out with this combo:

3 destroyer all shields
2 frigates, all engine killers

I only got 1 ship but that was enough. Rather than dropping the movementless ship they kept in the fleet and sat there for ages. Once their supply ran out and I had emassed a large enough fleet I sent in missile ships and boarding ships, gained a lot of tech.