Yeah, I'm not sure why the pirates can't use long range jumps or wormholes. They may be able to travel outside a system if it's just by normal phase lanes, so it's probably pathing, the AI gets into trouble on multi-star maps. But this shouldn't affect wormholes?
Another aspect of the pirates that might be an easier fix is that their asteroid is very weakly defended, if they are expected to survive late into the game. How about-
As it is already a 'special', the pirate gravwell could have a plasma storm or magnetic cloud, or both together? This would help... and the pirate base would look good against the backdrop. A plasma storm would be especially valuable, if the pirates continue to have no strikecraft support.
The pirates might use more defences- especially a stolen phase inhibitor. If they have to have just turrets, it would be fun if they had an assortment of turrets, not just all TEC, and perhaps some upgrades?