Well the Rome AI is a very different animal for the HoI3 AI. Doomdark considers it to be one of its best works. It set ups regions, builds armies to defend them fights in these regions. If a region is out numbered it gets reiforced. With HoI3 you have front lines, which makes things ever so slightly more difficult. However from a testing perspective the HoI3 AI was one of the easiest. Set up your theatres and observe. Oh look the AI is not transporting units, better get that fixed. There were a lot of bugs with the AI that were quickly spotted and fixed thanks to the theatre system. Making HoI3's AI in some ways in the best shape of any release AI. However the complexity of World War II made it seem inferior to the EU:R's AI or EU3's 1.0 AI.