My first game I was pretty much overwhelmed by pirates... (random small map)
Undaunted I started a second game without pirates, had lots of fun, close combat with the enemy and finally won (random small map without pirates).
Third game I went for a scenario... a TINY one...
It had my terran homeworld, the enemy terran homeworld. two astroid belts (uncolonizeable), two large asteroids (colonizeable), two ice planets... and a pirate planet.
I quickly mapped out everything, i was doing really well, holding positions. I managed to push out a third TEK KOL capital ship just as my two existing ones annihilated the enemy's only battleship. I was ready to go on the offensive in a pincer manuver that would give me control over everything and blockade the enemy...
Then the pirates arrive... at this point the enemy has his homeworld, I have my homeworld and a single astroid settled... the pirates fly by my fleets and start bombing the astroid with about 15 large cruisers... Those can take a single capital ship... they need two capital ship or a capital ship with about 10 small cruisers (and they will kill all the small cruisers and then just bombard while the capital ship finishes them off)..
Not to worry though, I brought my 3 capitals to bear and killed them... I try advancing and another wave immidiately comes... and then again... and then they started going after my homeworld... They blew up my capital ship and cruiser factories in orbit and destroyed half the planet (literally) before two of my capital ships could kill them... The third one had to deal with an enemy capital ship and 10 cruisers... and was killed eventually in a very close battle.
They pirates kept on coming and I gave up on the game... There was just no way for me to field a pirate defese fleet and an enemy fighting fleet... the pirates literally flew by the enemy ships and mine as well to attack soft core worlds. They fly fast, they jump fast, and they build huge fleets that they should not be able to pay for. (as far as I knew there was no bounty on me).
In a larger map with a few fozen planet/planetoids I would have probably been able to stomp them, but not on a tiny 6 planet/asteriod one...
I should have probably attacked the pirates with my 3 capitals or maybe attacked the enemy homeworld right away instead of trying a pincer maneuver to gain territory control... still. The bottom line is that pirates are not balanced for the size of the map... and also, what the heck kind of pirates are they? they seemed to have infinate wealth generated from some unknown resource...
The fact that pirates always attack with 15+ large cruisers also means that:
1. Planetary defenses are completely useless against them.
2. Fleets of small cruisers are ineffective.
3. It takes two capital ships to take out a pirate fleet. (I one managed to get them to engage a single capital ship instead of a planet... and they killed it!)
Heck I don't even get large cruisers until tech level 5 or something...