Grrediguts
One source ascribes Cassius Dio's omission to the terseness of his account, rather than to any uncertainty about the existence of Bar Kochba:
http://histories.cambridge.org/extract?id=chol9780521772488_CHOL9780521772488A006
But even that is much more than we have for Jesus. There are coins bearing Bar Kochba's personal name, Simon, evidently from the period of the revolt. There can surely be no doubt of his existence. Or, in fact, do you doubt that he ever existed?
Startling omissions by individual chroniclers are not even confined to the ancient world. Within a few decades of its occurrence, John Barbour wrote a very long poem about king Robert Bruce and the Scottish war of liberation against the English, one of the main sources of information about that event. Barbour never deigns to mention Bruce's predecessor Wallace, who temporarily evicted the English from most of the country a few years before Bruce's rebellion. But the evidence for Wallace's existence, and for his importance, is overwhelming. His historicity simply cannot be doubted.
One source ascribes Cassius Dio's omission to the terseness of his account, rather than to any uncertainty about the existence of Bar Kochba:
http://histories.cambridge.org/extract?id=chol9780521772488_CHOL9780521772488A006
So terse is the one extant historical account of the revolt, found in the abridged version of the third-century historian Cassius Dio's Roman History (69.11–15), that it fails even to name the rebel leader. Archaeological findings from 1952 to the present, mainly papyrological, fill the gaps to a certain extent; however, they by no means create a coherent account of events in Palestine during the three-year revolt. Emerging is a partial picture of Bar Kochba's leadership style and administration, his state's borders, Jewish observance under wartime conditions, and the strong Roman reaction.
But even that is much more than we have for Jesus. There are coins bearing Bar Kochba's personal name, Simon, evidently from the period of the revolt. There can surely be no doubt of his existence. Or, in fact, do you doubt that he ever existed?
Startling omissions by individual chroniclers are not even confined to the ancient world. Within a few decades of its occurrence, John Barbour wrote a very long poem about king Robert Bruce and the Scottish war of liberation against the English, one of the main sources of information about that event. Barbour never deigns to mention Bruce's predecessor Wallace, who temporarily evicted the English from most of the country a few years before Bruce's rebellion. But the evidence for Wallace's existence, and for his importance, is overwhelming. His historicity simply cannot be doubted.