My General theory here is this

A line of around 8 high valour arbelasters, 3 Allegion on the flanks and 2 Varagian guard for pinning.

The Arbelasters with cut down most of the mongol heavies, once they're all used up mass charge arbs and Varagians into the centre of the line and let the Allegion take the flanks. If you have a hign valour General then your enemy will usually break and run.