I know we don't know what engine DOW3 will run on but I am going to write some suggestions for the AI assuming that the same AI and ScaR is used for DOW3 as DOW2. I haven't played COH2 or cracked open those files so I don't know if these things were adjusted for that game. Obviously there will be some changes as buildings have been introduced.
I am trying not to put anything in here that is totally redundant in a new game (eg "AI builds too many heretics")
Firstly, the AI for DOW2 was written for the game at release and I don't think really took into account changes that occurred with the TiOW patch (except I think the pre-specified build orders were deleted). Also, players often play the game somewhat differently to how it is anticipated eg number of squads before teching up/building. I would suggest that an AI programmer is contracted to adjust the AI after the game has been out a while.
One of the main things that became outdated in the DOW2 AI was the teching up script. This was written to be dependent on the amount of red of zeal resource based on the game at release. After TiOW human players decide when to tier up when they reach the appropriate amount of power and number of units. The decision on how many squads they want affects the rate of power acquisition. The simplest thing is to increase the demand for a tech/building as soon as the power is nearly accumulated (AI will blindly accumulate power).
Thirdly, the thing that really frustrates me, is that the retreat scripting is done by SGroups. In a game with small numbers of squads and individually micro-ed squads this really needs to be done by Squad not Group. I can see why this was done due to the limitations in available functions but it is easy to run through an SGroup and select individual squads. Also retreat can be improved by making the threshold for retreat dependent on the relative numbers of allies and enemies and whether the squad is in melee or not and is a melee squad (ie non-melee squads want to run away very early from melee).
There are a few other minor issues:
-- All teleport abilities need a small minimal distance (or one needs to be scripted for the AI) otherwise the AI tends to teleport units recurrently on the spot in combat and use up their energy uselessly
-- The number of turrets the AI builds needs to be controlled as multiple are a waste of resources in DOW2
-- Artillery targetting needs to take into account nearby allies as there is a lot of "friendly fire"
-- Artillery targetting should take into account if a target is moving and lead a bit
Hope this is helpful. Or if you are using a new engine ignore it completely :-)