Let me first say that if your a historical accurracy prefer, then you can safely ignore me, i'm talking about balance points only.

Now then, yes Archers should be deadly to units. HOWEVER, from a balance point of veiw it seems it was allways intended that this WOULD NOT be the case vs. sheild units. Missile units where bassicly meant to be balanced along the lines of:

Good vs. 2-Handers and cav without sheilds, (i.e. late high power cav mostly).

Weak vs. Sheild and Cav with sheilds, (i.e. most early cav).

Their was never any intention of Bows being own everything units. What they where meant to do, (IMHO), is whittile 2-handers/late cav down enough that your spear and sword units can beat them.