I been playing around with the new AI difficulties, and I must say they have some short comings. I played a Ancient Gifts against 4 allied random vicious AI, and while I was surprised often by their sudden and unexpected attacks, and size of the attacked, the AI is unable to cope with star bases still.
All it takes to defeat said AI is to build a star base, upgrade it, and never look back, because the AI is unable to build the fleet needed to kill it. True, the AI did build anti-structure frigates, but never in the numbers to kill a star base, they generally make 6 max in their attack fleets. And they always attack the star base from well within their firing range, allowing the star bases to pick up the anti-structure frigates. Their needs to be some sort of threat assesment abilities of the AI. They need to be able to sum up the planetary defenses, esspecailly the star base, and send the appropiate fleet to destroy it.
And that brings me to another point, the fleets rarely ever meet up for a attack. Its very common for human opponents to wait to attack for a allied fleet to arive. At higher AI levels, this should be COMMON behavior. The AI also needs to incorporate focus fire, and the appropiate counters. The star base example is the best. Vasari AI should attempt to star base a fortified planet at the very start of the assault, and a advent should have a very large numbers of bombers to cope with star bases, because advent anti-structure frigates suck at that job. Tec AI should also have the required number of orgov, 6, as in typical AI behavior is not enough. Double or triple the number is required to really have the AI destroy a star base.