It is still too easy to conquer the AI because he does not garrison it's planet enough.
Could you add someting like this in GalCiv3GlobalDefs (or FactionDefs) :
<AIGarrisonLevel>0.2</AIGarrisonLevel>
<AIGarrisonLevelAtWar>0.35</AIGarrisonLevelAtWar>
AIGarrisonLevel would be a percent of the Planet Class: It would tell the AI to keep at least this amount of garrison on the planet.
