If you are looking at writing an AI, and you are considering doing one for TripleA, this post might be interesting
A good hueristic for an AI is a really difficult thing, and I am not even sure that devising one will help with writing an AI. The branching factory for a game like Axis and Allies is so huge that assigning a number to nodes in a search tree (no matter how carefully pruned) doesnt seem like a good idea.
I think looking for patterns like dead zones, transport bridges, infantry pushes might be a better option.
But like Octopus said, I think one of the keys is to just write something that works first, then write something that can beat the original ai, and just keep improving. Trying to start with a human beating ai from the first revision is a real challenge.