One of the main issues is the time era the game pulls from - During the early middle ages the bow was extremely effective - Although an archer HAD to be properly trained which made them less numerous than the common levy infantryman almost no Kingdoms/Tribes at the time had professional armies, forget about combat trained archers which is why many nations chose the crossbow over the bow as it's operation required less training despite it being a more complex weapon from a construction standpoint, which again made them rare too.
Wrought Iron was still a common material for armour and plate was still a few hundred years off. Mail was great against slashing blows and thrusts from most broad-tipped weapons but the bow, repeated attack with a spear and early sheer impact of the Norman lance (Due to their innovations in saddle design) was still extremely potent against mail (which is what brought about development of better thrusting defensive armours). And mail was mainly a nobles and their guards armour at the time your common levy infantryman would be lucky to have a helmet of simple banded rivoted construction to go with their shield in most Kingdoms.
From a gameplay standpoint well trained archers should be extremely rare, high cost and maintenance and very precious as they should be a rarity. The general accuracy of archers should be lower with a lower fire rate. Very few nations had archers capable of firing more than 6-10 shots per minute even on recurve, self and composite bows, forget about longbows (Exceptions I can think of off the top of my head would be the Welsh and many of the Steppe tribes) and the highest threat killzone of a bow is within 200yds, losing high amounts of men beyond that range is a bit harsh on infantry units and the bow shouldn't stunlock infantry, especially in a shieldwall.
TLDR: Infantry should definitely take less casualties closing on archers and those archers should not be shooting like machineguns.