Magocracy in any game is devastating and you must have done a great job of that in your game.........however i myself have't accomplished such a devastating magacracy before and big summoners like yourself fit in wonderfully in the FfH scenario liches and all.........the bad guy in that land over there, ya know the one to conquer for the sake of our children and grandchildren.......
Point being, play hotseat and see what can be done vs someone like that and see what strategies work on which don't because most of the things summoned have promotions to defend against them, more challenging yes, undefeatable no.
Good job regardless, you made a magic weilding conquer driven empire that vanquishes its enemies

and your post has given the Team ideas about AI changes I am sure not to mention those that are in the works.

.......that new magic user AI and its potential growth already scare me and now I am not sure what will happen when I go to sleep...........
Sooooooo, If summoning is too powerful and the things I summon get defeated often so I don't fully relate but even if the team wasn't going to looke at things that way my post doen't help either

and look at the aveatar....so i hope that summoning isn't reduced, I just hope defense against magic developements increase.........