. Armour and Evasion:
For purposes of realism and balance, a hardy knight's armour should deflect arrows with relative ease and minimal damage (except on critical to exposed areas), where the Samurai and Vikings receive moderate damage to most areas depending on location hit (and how complex the game's hit detection is). Though those factions with less armour should have their own counter.
Smaurai could have the ability to dodge or deflect arrows (
yes, for the most expert warriors, this is possible,). These abilities could come as feats, in that a certain feat would give a passive percentile chance to dodge arrows, where another may provide the opportunity to press a button moments before being hit to knock the arrow aside, though the logistics of this second suggestion may be complicated.
As for Vikings, aside from passive feats as mentioned above, it may be that Vikings have to employ shields against an archer-heavy enemy. This rock-aper-scissor effect is fine. - that Vikings may be weak to archers compared to other factions.
. Ammunition and Fire Rate:
To suggest a refined number of arrows per archer would require me to know more about the game (maps, arrow damage etc.) though I would start by suggesting around 16-20, certainly not akin to an FPS where you'd be given 30, but also as low as 14 seems too few to me.
Fire Rate will affect this too. I believe the time taken to notch and draw the bow should take around 1.5-2.5 seconds. It shouldn't be as fast as we see in other titles, but not so slow as to undermine that these heroes are masters of their craft.
A longer time spent in full-draw should reduce accuracy too, and to quite a significant degree. Though the following video is a joke, it's a good example of how mainstream entertainment directors/devs often skip over the fundamentals of medieval weapon logistics - something it seems that this game has promised to implement (Art of War mechanic).
Video
. Additional Effects:
A warrior stuck with arrows might not take too much damage depending on their armour, but being hit with such a force can leave deep bruises, broken bones and concussions. Maybe, to counter the suggestion that arrows inflict lesser-moderate damage, they also induce debuffs such as reduced stamina/speed, reduced attack damage, possibly even a blurred vision amongst the edges of the screen upon taking and surviving a headshot (which could dissipate over time - like 15 seconds or so).
An arrow might also stun a warrior's charge, or provide an opening for an ally locked in combat.