Let's just say that Josephus, like all ancient historians, documented history differently than modern one such as John Keegan or Rick Atkinson might do today.
I'm inclined to swallow most of what Josephus is serving because his is a contemporary account. However, there are archeological contradictions to what Josephus wrote. I think the story of Masada is credible but legitimately problematic. I'm not willing to disbelieve an original source historian unless a modern revisionist produces tangible evidence to the contrary. The absence of something does not prove it's opposite, as "History of Terror" might claim.