At first: I'm not interested to turn this into another "the AI is broke"-thread.
But as far as I understood (the developers), the AI not building castles is considered a bug and will (hopefully) be fixed in the patch.
So if at least some of us
can agree that specially tailored race could help the AI, maybe we could gather some suggestions ..
I for myself don't know that much races well enough, as I'm only playing S&A Tien'Chi and Tuatha at the moment.
But I haven't tested if the AI can get along with the special requirements of these themes - does it buy Danoine Sidhe, or does it summon Heavenly Deamons? Both would greatly benefit from blessing, by the way ...
Here's on of those AI-races I had some success with in DOM1, tweaked to fit the changed castle cost:
# Arcoscephale ########################
Shedu
Astral 5, Earth 4
order +1, prod +2, growth +1
DOM 5
castle 30/150 (60pts)
6 left
#######################################