I finally got around to making a forums account so I could comment on some of these things.
I generally play AI War with my wife and a mutual friend, so we're doing a multiplayer game with 1 homeworld each. We were previously able to play on difficulty 9 with some success and actually had a foray in a difficulty 10 where we were making good progress on it.
... (snipped for length)
Hey. Welcome to the forums!
First, for the most important question, what version are you playing? Several of the balance issues you mentioned have been played around a LOT in recent betas, fixing the worst of them.
About those hundreds to thousands of bombers, what are you doing to prompt the AI to send those? If it is something you triggered, well, don't do it. A big portion of AI war is learning to know what causes the AI to send "death blobs" at you and then avoid doing that.
I would agree that armor type bonuses are still a little too much of a factor in determining DPS. It's a LOT better than it used to be, but there is still a feeling over "overspecialization" of many ship types. For example, the point you made, pretty much the only fleet ships that have any hope against force-fields are bombers (or any other ship with similar armor bonuses). The balance against various types of armor, in particular structural armor, is still a little too emphasized on armor bonuses. Keep in mind though, just like in many RTSs, some units are supposed to perform AWFULLY against other types of units, so this behavior is supposed to be seen a little. (like machine guns vs. tanks in Command and Conquer, even several dozens of standard 1st tier gunning infantry are supposed to be a joke against a single well armored tank)
And what Mk. force-fields have been letting you down? Mk. I force-fields are sort of a joke, but they are supposed to be a joke. Only the Mk. II force-field and up is supposed to give you any real protection. (Though until recently, they were failing that, so they got a good buff)
About the carriers, the invincibility thing was supposed to help improve performance, to stop you from popping the carriers and releasing a bunch of ships and slow down the game until you kill some other ships first. It is sort of annoying, but carriers are supposed to have very weak guns or something, so you would want to take out the "real" ships before popping the carriers anyways. I have not seen much of carriers, so I don't know if the carriers themselves pose much of a threat.
As you mentioned, the AI was a lot easier up until recent versions. There were many bugs found that were stopping the AI from doing what it was supposed to do (such as retaliating properly, the first wave was getting ignored for some reason, etc.) Now that these are fixed, what was easy at lvl. 10 is now really hard. So that was due less to balance shifts and more to the AI doing what it was supposed to do in the first place.
Well, I've just said a lot, so I'll shut up now.
P.S. Where did you find a wife that plays AI War?
That's awesome!