From what i know about archers, they were quite important for some civs.
Look at the Persians and their "ancestors" the Babylonians and Assyrians. (before the timeframe of RTW, but what the heck), their armies consisted out of: (correct me if i am wrong) many, many HAs, much heavy cavalry, good footarchers, and only light/medium infantry.
It looks logical that the Persians just bombarded their enemies with arrowfire, and if that would not work, they just used their awesome cavalry (chariots too?) to finish their foe off (again, i am not sure, but the Cataphracts in RTW are Persian "ripped off" units). Their infantry would just be their to pin any lucky fool that comes through the arrows, and finish it off with support from their cavalry.
So, if this is correct, Persians relied heavily on missile units and cavalry. Thus this is "evidence" that archers were very important for the Persians and other civs.
Dont be an Onager, use one instead.
"The Pope? How many divisions does he have?"- Joseph Stalin