Well, most the Jedi in that fight sucked. They were the kind of Jedi who never left the temple and only trained enough in combat to say they trained. Nothing wrong with that. Their role was academic or social or anything but military.

As a form, Niman was “just enough” to not be totally useless. (It was still mostly useless, the whole point was it was simple for Jedi to learn allowing them to focus on other things.)

They were also severely overwhelmed and it was a math game- if a Jedi could deflect 50 bolts a minute, 51 bolts would eventually kill him.