1) I recall there being issues with very large armies storming a castle. But we're talking in the thousands range. That just isn't very likely to occur unless you're playing Ermor. For all practical purposes it just isn't a problem.
2) Already has been answered.
3) Like some others in this thread, I've played games that have lasted months, and a few which I finished in one night.
4) The AI is actually quite reasonable considering the scope of the game, which is huge, and has more aspects and situations than probably any other computer game, ever. There will be various occasions where the AI will do something suboptimal or you're wonder why it did that. You can console yourself by thinking that not every opponent you will face in dominions has to be a tactical or strategic genius. On the other hand, if Dominions possessed a vicious and powerful AI on the scale of how strong Deep Blue is for Chess, I imagine a lot of players would no longer have fun and stop out of frustration. Anyway... If/When you start beating the Impossible AIs, you can then do some things to improve the challenge.
By no means a comprehensive list:
Personally, for example, I use and suggest a handicap of never hiring mercenaries.
Another suggestion is to play with a lower resource setting (it helps the AI spend more on it's national troops and less on independents)
Yet another suggestion to take that last idea a step further, is to play on a no-independent map, or use the no-indep. mod.
Furthermore, you can start a game, and just not do anything for the first 5 turns. (Or 10, or even 20.)
Finally, one can always mod the game, nations, units, spells, or maps to give certain advantages to the AI, or simply work better to fit it's style of play.
SuperSecret Tigerdragon DeluxeEdition Suggestion: You could always play against other humans. Though I realize that this is outside the scope of the topic, it just had to be included.
