Sweboz Battlefield Tactics, AKA "Quinqtillus Varus..."

[athanaric]

You can't hit the mighty Horse archers in real open field combat!!!

You can. Advance Roman-style with a charge-proof checker-board system under heavy cover fire. Hit their HAs with foot archers, and the Noble HAs with slingers. Bring some Skythian HA mercs of your own, and one or two units of Teceitos, falxmen, or clubmen to take out their FMs (who are immune to arrows).