Hey
first thing: when the pirates attack one of my worlds wich has trading posts they will attack those trade ships instead of my fleet and defenses. the pirates are then to easy to destroy.
second thing: i was wondering about the envoy, i tried to get a cease-fire with another AI computer but they kept attacking the envoy. wich was only doing them favors....why would they destroy something that does favors for them. this sometimes makes it impossible to get allies i think.
My suggestion: envoys cant attack. they only benefit the AI planet. why not make them neutral (you cant attack them), instead of the invulnerable shield skill.