If you have a series of weak parallels that are easily accounted for by coincidence, generalization, and confirmation bias, then the end result is a weak case for intertextuality.
The argument needs to proceed step-wise through a series of stages, and it is a non sequitur to assume one step readily follows from the prior. Establishing that a particular gospel probably utilized Josephus does not determine that all did.
There are a series of stages, but if people are unable to acknowledge the similarities and evaluate fairly a good percentage of the parallel set then we cannot proceed.
But then there's also the question as to what are the criteria for determining intertextuality. Without having some rules of thumb here, how is the argument advanced if my interlocutor simply asserts I am too "granular" and I say that he is too woolly?
Atwill contends that there is a typological relationship between the works of Josephus and the Gospels. In his understanding, the chronologically prior events of Jesus' ministry ca. 30 CE are presented as the type and Titus' military campaign is presented as the antitype. So far so good, except of course that Atwill contends that the same circle of elites is responsible for both sets of literature.
One should keep in mind that this utterly unique proposal lowers the probability of his hypothesis, because this would be the only known instance in which, in terms of actual production, the proposed type is generated after the antitype and by the exact same community.
Luke 1: Castiel went to the bar and ordered a drink that was red.
Luke 2: 3 guys had lipstick on their lips in the bar and were lying on the floor.
Josephus 1: Castiel's favourite drink is tomato juice.
Josephus 2: Castiel gave 3 youths the "Kiss of death"
16:00 - A Westerner travels to North Korea and is wearing factor 3 sun cream
33:00 - The Westerner takes off a pair of trousers
62:00 - The Westerner walks past a department store and sees luxuries
73:00 - The Westerner is told by the tour guide about the leaders of the country
84:00 - The Westerner travels back to the US
16:00 - A native visits a capital city and sees 3 giant posters of men
33:00 - The native is told by a police officer to change one item of their clothing
62:00 - The native enters a shop but is told nothing is for sale to anyone but they are only there for show, for sake of the foreign media.
73:00 - The native makes a jibe about one of the men in the posters
84:00 - The native is not allowed to return home and is instead taken to a prison camp
All the above parallels were created by me from both sides. Now, if you look at them too granular then you will miss the connection and satire.
Here's one of the more bizarre Flavian parallels that I may not fully understand yet as I am still researching:
Some other gospel translations/variations have different details:
43 Now a woman, having a flow of blood for twelve years
47 Now when the woman saw that she was not hidden, she came trembling; and falling down before Him, she declared to Him in the presence of all the people the reason she had touched Him and how she was healed immediately.