Knights may have been well protected, protected to such an extent that being killed by an arrow was more down to the archers luck than a certainty. What is often overlooked is that the majority of soldiers were not knights, and were not protected to the same degree.

A feudal Levy dictated that a knight answer a call to battle and bring along a certain number of men at arms. these soldiers were maintained at his expense and were always availiable. since a suit of good quality plate armour was very expensive, he would equip his men either with older armour, or with armour of a lesser quality.

so in battle, a unit of 'knights' on foot or horseback, would have been made up of a number of well armoured knights, and their more numerous, and not so well armoured men at arms. Arrows were far more likely to kill the men at arms than the knights, which is why so many knights were captured by the english, the men at arms generally had arrows sticking out of them.

as to the claim that longbows are no good IG. well i feel i must disagree, i am of the oppinion that one should maximise your strengths, and the english ability to field longbows is one of them, so instead of having a fairly conventional 3-4 units of them, i take 10-12. in that quantity they are quite, quite lethal, certainly lethal enough that my fairly outnumbered heavy infantry can adequately deal with any enemy that get through, and they have the added advantage that you can make your battle line fairly horse proof

regards