Also, AI needs to put higher weight on the Magic Winds wonders, or on Education, Universities and Observatories. As the empire without much of a tech lead I'm able to acquire and build all of the Winds techs despite 10 AI players (ok, minus the two I killed), which lets me build ridiculous numbers of mages and to field truly heinous numbers of tier3 archmages.
Count up all their high level units, they get far more than any other faction (though obviously most factions aren't done). 3 steamtanks, 10 handgunners, 10 cavalry, 10 knights (plus more for grail knights), unlimited halbards, 3 ironclads, 10 longbowmen, 10 crossbowmen, 3 Greatswords, 5 great cannoncs. Compare to Woodelves, another "mostly done" faction who get 10 longbowmen, 10 knights, 4 eagle knights, 1 treeman, 5 boltthrowers, 3 royal guard. Anything else?
(Might be wrong on a few of these and missing some units).
*Edit*
Missing war chariots, and griffons/unicorns.
Also, rather than war chariots, could the Empire get Imperial War Wagons?