Interesting observations...
I've seen Marg using Summer Lions by turn 20, two summonings worth. I've seen small amounts of undead in Jotun and Ermor (go figure...
) The tac AI likes to summon during combat though, but that's not really the same issue...
I've also noticed that the AIs seem to have really bad gem incomes (compared to mine anyway). Its a bit difficult to tell how poor they are since mine are often giganitc, and there's no scale to measure against, well I guess its reletive and the bottom is zero... I'm just to lazy to do that math
I've seen some mages in enemy armies, but I've not seen the enemy do alot of searching, though usually when I do hit a province that has sites it has 2 or 3... does the AI cheat at all in knowing where the sites are? (probably not, but it seemed strange to me).
There has been alot of productive discussion about the AI and army composition. Though many of the suggestions may not be workable, I think the key point is that the formulas that control the ratios of units and also commanders should be looked at again. The formulas for fort, lab, and temple building are connected to the AIs ability to field different unit and commander mixes as well, so they need to be taken into consideration.
Really if Illwinter were able to externalize those forumulas so that they could be tweeked by mods I'm certain that the community would quickly create tweeked formulas to give the AI 'better' army composition. I'm also certain that Gandalf would figure out some way to randomize the values in the formulas to make a skitzo AI that might or might not 'whomp ***'