[Aleph]

Read about five pages of this and had to go, wanted to post:

Agincourt, AFAIK, was partly won due to a simple difference in philosophy. The French thought that they were fighting a chivalric war and could expect to be captured and ransomed back if defeated, while the English were well and truly in enemy territory and took to murdering the surrendered French knights with daggers and sledgehammers. It's like if one side of a football game all came to the field with brass knuckles and knives and there were no refs to call foul on it... you'd expect that team to do quite well until the other side caught on. This is a problem you won't have in Dominions - there's no honorable surrender.

Furthermore, AFAIK the French didn't even bother deploying their crossbowmen at Agincourt. Certainly, they might have fared better if they had.

Finally, I believe the longbow was never outlawed for use against other Christians by the Vatican, which tells you that the crossbow was doing something right.