Thank you for the list of independent anecdotes and factoids. But what is, in the context of this thread, your point?The problem is basically one of preconception. Firstly, we're guided by our ideas of modern military expectations and please note how easily people compare ancient and modern in that context. Secondly, a great deal of commentary on the legions starts from the idea of their military excellence. Well, they were certainly capable of making an impression, yet documentary evidence suggests this was not uniform. After all, they did not even have uniform appearance in the manner we typically portray them - shield shapes varied between legions and in one source (Stratagems by Frontinus if I recall correctly) a legate criticises a soldier for his elaborate painting of his shield - "He cares more for his shield than his sword"
Since the Roman legions were not regiments of an army organisation (they were all independent packets of military power assigned to politicians to further security) we ought to look closer at relative performance and loyalty, important issues to them politically but less to us when enthusing about excellence.
Thirdly, concerning discipline. In modern terms we expect "organised good manners". Observance of rank and authority, esprit de corps, behaviour (though we all know soldiers have a tendency to misbehave ). In Roman terms, their discipline was harsh and not always consistent. Basically they wanted obedience and steadfastness. usually, as with most pre-20th century militaries, they got what they wanted because the soldier was more afraid of punishment than misbehaving. Nonetheless, the sources are quite clear. Roman soldiers did rout. One of the tasks a senior officer concerned himself with in battle was not necessarily directing them, but standing behind a wavering unit pushing men back into line (Caesar describes this in his Gallic War commentaries). A leader might well fight in the front line alongside his men.
Still, we can see why this mattered. A Roman legionary can be executed for refusing an order. He can be flogged for petty offences. Their regime, as Josephus confirms, became one of constant practise when legions were properly led. But were they the best? More difficult, because our impressions of Roman soldiers are from the Romans themselves. We have little comparative evidence.
I'm reminded of an anecdote from Plutarch. During the fighting in Britain a legionary spotted a group of centurions under threat from British warriors. He ran to their rescue across the marsh, dropping his shield (a serious punishable offence) and saving the day. Caesar saw what happened and summoned the man to him. The soldier arrived and dropped to his knees, begging for mercy. Caesar wanted only to congratulate him for his bravery.