Over many years, I have had many tough, challenging games against Athena. After reading about some of the horrendous AI problems experienced by others, I realized that I rarely run into them, the main exception to this being the Stack of Doom. I looked at how I play, and I thought it might be helpful to share some things.
I use the AI settings recommended by the developers, and I usually give the AI more time.
The most important thing I do is this. I act as if I am facing a human being, and only make moves that make sense according to the situation and what armies actually did during that period.
The second most important thing is that I only give orders that make sense according to the military realities of the time, protecting key areas, trying to stay in supply, etc.
I do not study Athena to see what her weak points are, I just try to play the strategic situation as if I was facing a human general. for example, I protect every key point that might be vulnerable to a human general, without even trying to find out if Athena might ignore it.
I do not engage in exploits that will drive her crazy, as they involve maneuvers that no real general would ever make.
The stacks of doom are still a problem, but not in every game, and I have hope that the solution proposed by Kensai will be adopted.
My final point is this - If you treat Athena with respect, and pretend she is a real general, she will give you a challenging game where most of what she does makes sense. And while I usually win wars, I have suffered many defeats, and lost some wars and games to her.
Just my two cents, but I hope it helps someone enjoy these games as much as I do.