Thank you for the feedback Teyrn Leto! It's nice to hear something good about our AI when most people are like "It sucks!!! It doesn't work in multiplayer! It doesn't build anything!"
I'm glad to hear the balance is good, I made the missions harder than they originally were by making them train soldiers faster. I just guessed some numbers that seemed about right, but I was worried I'd end up making them impossible.
Yes The Dark Lord is right, they attacked your gold mines because those were the closest buildings to their village. I'm not sure why the groups would get smaller. Obviously they'd run out of barbarians, but they should still send the same number of men to attack you.
There is actually a bug with the AI in r2678 that I fixed yesterday (it was also causing a crash) which makes them allocate groups strangely and usually end up with a very large group at once place and no groups at the other places. I'd be interested to hear how the AI goes after the next update.
P.S. I'd love to see the replays

I want to see what effect the bug was having later in the game.