Unfortunately I don't have a savegame of this but I was recently playing a game, Small galaxy, me and the two other races. We were all plodding along, the AIs were at war and I was very near having 75% influence (I actually got it at one point, but before the victory condition timer thingy could start one of my stations was destroyed). I left Events on because I usually enjoy them, one of my favorite is (coincidentally) pirate attacks, because I keep my military at a level where I can't sustain a full blown war for long but can hold off any attackers.
In this case each of my planets had 3 ships with 2 attack and 1 defense apiece (mass drivers and armor). All of my stations had the barracks and 7 attack laser upgrades, so they were at 8 attack, no defense. The most powerful AI fleet I ever saw (and I was between the two fighters, so I saw most of them) had 8 attack and 2 defense.
All of the sudden an event happens, Pirates all over the galaxy, I just go on with the game, expecting them to be the standard weak pirates and for my defenses to hold. One fleet of 3 pirate ships attacks one of my stations...and destroys it, surviving. This left me a little unhappy, especially since the enemy destroyed a station I had stationed units at without attacking the units, so I went to take a look at their stats. 55 attack, and 6 defense. There were about 10-15 pirate fleets with between 30 and 60 attack running around a galaxy where the strongest non-pirate ship had <10 attack. The game was pretty much over at that point, while the pirates couldn't conquer planets they did destroy all of my stations (knocking me down from 75% influence to 51%) and then proceed to camp all the planets, stopping any and all ships (there were less than 15 planets in the entire game, I like small games). It became a simple game of who could research their way to victory or to being able to beat the pirates, and that wasn't the game I wanted to play (I wanted a Terror Star and influence victory, research victories are too boring for my tastes).
Is this expected behavior? I would imagine that pirate attacks should be scaled to the current state of the galaxy. Considering my fleet was 30-50 ships with 2 attack, and I had the best military rating (200 points), having even one fleet with >50 attack spawn would seem to be an event in and of itself, 10 of them is just absurd. Besides that strange, and extremely annoying occurrence, however, the game was quite enjoyable. I'm just worried that the next time I see pirates attacking I'll have to quit the game because it'll be over.