Troops vs magic, what am I doing wrong?

[cthulhu]

Late-game AI on impossible difficulty will wipe through 125 PD without effort. 125 PD w/ a dozen decent battlemages backing it up though will stop most late-game AI armies, but will suffer occasional mage casualties to enemy fliers and spells and be defeated occasionally by particularly strong armies. Also useful for stopping AI armies in defensive situations: PD + half a dozen battlemages + some middling zero-upkeep-unit-producers (unholy priests, fairy queens, whatever). If the province gets left alone for a while it will start building up a few hundred zero-upkeep no-need-to-eat soldiers, which should hopefully make it impossible for the enemy to take it later on as long as the combat mages stay to support the troops.

In my experience vs AIs you generally want troops until about research levels 4-5, then a mix of mages and troops (possibly using PD or summoned troops to minimize upkeep) until research levels 8-9, then an end-game strategy (massed clams if not using a mod that makes them unique, massed juggernoughts, massed vampire lord or wraith lords, some wished up seraphs or chayots w/ full items).