That's interesting...Playing Venetians at the mo (looking forward to unlocking the byz) mostly battles with byz armies have so far gone something like:

byz: "deploy our vaunted horse archers! haha, those sons of dogs won't know what hit them!"

venetian1: "was that some light rain, sire?"
venetian2:"nay, the byzantines fire upon us with tricksy mounted archers, show them what for, men - send in the knights!"

*SPLAT*
...

*whimper*

"methinks the byzantines will trouble us no more,sire, though that militiaman did bleed awfully on your nice heraldic tunic..."

Can see there being problems with larger than the rather pitiable numbers the AI has so far fielded, though...