This distills the AI governing enemy focus and movement into a flowchart form that should cover 99% of situations. Isaac looked at and approved version 4. You can also view the most recent version here: https://docs.google.com/drawings/d/1F5YcJz4sY8tVP86cH6MS2x4n...
Here is the original forum post with detailed discussion on movement: https://boardgamegeek.com/article/25343712
Thanks to the following users for their help and suggestions: countertorque, alphasquid, Daemon6, mfaulk80, davidglasser, GAFBlizzard, Vehementi, Breegull, MrTroy, logris.
Version 6 clarifies a few common misconceptions.