We know that arrowfire alone was more than capable of turning back attacks large and small.
If so then why did English used difficult terrain and field fortifications? If the firepower was enough to drive the opponents off they wouldn't need them. If English longbowmen really had such firepower how come French started dismounting? Massed infantry is far more vulnerable to any kind of fire than cavalry. Shouldn't they be shot to pieces by archers?
In 1352 at Mauron in Brittany, there was a quite a large battle between Guy de Nesle’s forces and those under the command of Sir Walter Bentley. The standard English formation was countered by dismounting two of the three battles and placing them in the center and one of the flanks while third consisting of around 700 men remained on their horsebacks. The French cavalry charge was successful and they managed to drive off the English archers deployed in front of them. In the meantime, the two dismounted battles in the center and opposite flank not only managed to reach the English line and engage in melee but even pushed the English men-at-arms to the back of their fortified position. Unfortunately for the French their commander de Nesle, got himself killed after which the English counterattacked and managed to push the French forces away. The French cavalry, however, managed to safely retreat with minor losses.
This battle nicely disproves one of your statements:
Anytime Longbowmen had the chance to set up defensive works and could plant roots, they were impossible to dislodge.
Apparently, the French cavalrymen at Mauron didn't know that
In the battle of Auray in Brittany, in 1364 Bertrand du Guesclin also tired to advance his forces while dismounted, only this time they've been equipped with pavises to further protect them from English archers. One again French forces managed to reach English lines but ultimately they lost hand-to-hand combat. Their commander was captured while French forces routed.
The French opening cavalry charge in the battle of Agincourt also manage to reach English lines despite their firepower.
Summing this up, maybe "you", whoever you guys are, know that arrow fire was enough to drive off attacks large and small but I think that the matter is far more complicated. The key to English victories lays in their stance and position represented in using difficult terrain and field fortifications as well as their discipline AND of course their firepower that caused some casualties and disorder. This mixture allowed them to repel any attacks which in case of feudal armies (at least some of them) was enough to rout the enemy.
You do not have records of formations of archers of any other region in Europe performing these same feats outside the English.
Riiiight... Absolutely not. I mean, the battle of Nicopolis in 1396 definitely never happed and Janissaries definitely weren't using a very similar tactic in many, many other battles in Balkans and Central-Easter Europe both earlier and later.
Also Hussites, they definitely didn't use field fortifications in combination with high firepower and other troops in support to win battles. I mean, both the Hussites and Turks and didn't have longbows! No wonder they never made a mark in history, right?
Ok, seriously now. Marshal Boucicault who commanded the French in the battle of Agincourt was also commanding Fench troops at Nicopolis where he learned his lesson about the archers holding defensive position and supported by other armed units. What he tried to was the further development of the tactics employed in the battles of Mauron and Auray unfortunately for him everything went wrong at Agincourt. The flank charges were undermanned and cramped for room and were effectively neutralized by the defensive stakes; their missile-men were not utilized but were rather pushed behind the vanguard of men-at-arms whom they should have been supporting. The attacks on foot were swept by archery, blunted by the mud (with the resultant exhaustion of the men-at-arms) and repulsed by the relatively fresh English men-at-arms. (once again, it is proof that English tactic was relying on combined arms rather than the strength of archers alone).
So to quote you again on longbows:
unique weapon common only to English armies that gave them a significant tactical edge and was the primary driver of battlefield success for them when given a chance to deploy and defend a static position. This is not even disputable.
Although you are right that this weapon was or less common only to the English (cough, cough Welsh cough, cough) as evidenced form other examples of defensively deployed missile troops who managed to get similar results without longbows. English longbowmen were most definitely more dangerous than their counterparts from other European and non-European regions but it is commonly overstated as their firepower was definitely not enough to win a battle. They relied heavily on terrain, field fortifications, discipline, and combined arms tactic.
I don't think that in the game they should be in any way more special than having above-average quality. Especially that longbow already exists in the game files and it seems id does batter than "regular bows" against heavier armor. I'm ok with this depending on how much better that is.