Leshma, who as far as I know is not very experienced with shields, has aknowledged this basic fact most archers posting on the forums never care to admit for some reason.
I'm a bad shielder, however I do have 1 shield skill which isn't much but in combination with Old Heater Shield and some manual shield positioning it's enough to block most arrows that are fired straight at me. Although crazy STR archers do trash my shield in 3 or 4 arrows.
I do have some experience using a shield against archers. Against better archers (weasels) it's not useful because this is what usually happens:
1) they run and I chase them, i'm slower because of the shield but i'm still fast enough
2) after some time i catch them but they do 180 spin (which should be fixed) run straight into me, disrupting my attack
3) keep running in other direction
I don't have fast enough reflexes to release my swing before they run into me and I don't have a crystal ball to tell me when they are about to turn around.
Cocky archers do something else:
1) they run
2) let you catch them
3) shoot you when you're changing from shield to weapon
For high agi chars it's better choice to chase them without a shield than with it.