the funny thing about pirates (nice necro btw), is that if they win a battle, the survivers head back and reinforce the pirate base. In a long game, where the ai doesnt bother resisting the pirates, it means that you will end up with ALOT of pirates at the pirate base.
What version are you using? when you made this thread in 2009....., you certainly could not have been using diplomacy, where the pirates are EVEN TOUGHER.
hell, before diplomacy, pirates were free exp.
so basicly... I am very impressed with your low member number and your noobishness.
edit: oh, hey, look at little avatarless me on the first page answering your question 2 bloody years ago.