Quin, I may come as a bit condescending... Hell, I am condescending. Dominions 3 AI is beyond retarded. I must have played hundred MP games in Dominions 3. I stopped because my not-yet-wife asked me, but not before I won the first two official tournaments, not before the point when people were ganking me four at the time, and still losing... and not before I came up with quite a few strategies that forced Illwinter to change quite a few rules. Thanks for reminding me of that game, and making me revisit the threads for my most fondly remembered games.
I played Dom2 and Dom3 for years. In all that time, I must have played 5 games against the AI, unless you count a few turns to test a new pretender (against another side played by me). The AI could not deal with super-combatants, could be lured again and again into undefended territories and be wiped out for 1 gem, could be pushed into wars with other AIs, did not know how to use province shields, etc, etc, etc...
In 2008 Dominions 3 had NO single player, for all intents and purposes. I know of no good player who would bother. This may have changed, but it would really surprise me.
And the reason for this is that everyone who played it, played it for the multiplayer. And when someone wanted to drop, it was considered really poor form to switch to AI instead of finding anyone, including a newbie, to take his place.