How about letting shield block having a chance of blocking fired weapons? From what I remember, it's basically a free hit without any commands. Fired weapons also doesn't take up an important slot. In fact, arrows don't take up any slots.
From a rp perspective, it makes complete sense. Anyone who has seen Gladiator can't dispute that. It's doesn't make sense that shield block CAN'T block arrows.
From an balance perspective, it makes sense as well.
High chance to blow while in combat, low chance to blow while out of. (whos to say I'm not shotting arrows at you with your back turned?)
So I can parry, dodge, shield block, weapon block ALLLLL those attacks but can't block a measely arrow?
...Ever?...
Don't underestimate how accurately someone can fire a bow at point blank range while wielding/dual wielding weapons and aiming with his second pair of arms and firing.
I think they should be ranged only. This point blank stuff should either be under penalty, or require a class selection to do. Maybe only the archers get "point blank shot."
Oh, and on topic, shield block should definitely have a chance to block arrows. To the point where I would love to see even another factor for them. Shield size. Big shields block different attacks better than smaller, lighter shields.
I think that dodge should have a chance of avoiding arrows. I really don't want to see communers with immunity to arrows also.
I think there should be a shield expertise (as a normal choice) and it should grant 100% protection from arrows, along with the prof bonus.
Shield expertise-lore definitely...actually make it a useful lore! I've tried it..it is as bad it looks. :S
I REALLY want to see melees having a reason to use shields, besides when they are horribly unequipped and dead anyhow 
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I could be drunk a lot when playing, but I could have sworn I've seen people dodge arrows before.
If you're armor class is high enough, they might miss an arrow.. but it might also have to do with their respective fired weapon proficieny and any level advantage you hold over said opponent, plus the bow of choice!
This gives me an interesting idea, warriors should have defences lores.
Shield mastery would alow arrow block.
Dodge mastery would alow drunken dodge acess.
Two handed, decapitate or weapon cleave.
Ugh, warriors do NOT need weapon cleave. shudder
Aabahran