I wouldn't mind if the pirates would be more active:
- Visiting an colony and demand money (or they bomb you)
- hit an run attacks where they try to capture ships from you (assault shuttles, docking collar, fast engines) and then retreat with them.
- generally I would expect that the pirates would retreat if they encounter a superior force.
They do not fight for king or country but for opportunistic self interest, so no need for heroic sacrifices.
Maybe take a note from Civ barbarians : spawn occasionally some pirate fleets out of the blue to keep players busy and not get too complacent
Bonus for the human player faction: the human pirates go easier on you, but are not necessarily friendly.