After mucking about with other folks, this is basically Assault v2, except rather than climbing ranks, you clear 4 sections of one path to get access to a boss fight, which resets once you attempt it.

It's also very, very, easy. Easier than Assaults themselves back at 75-cap, at least for the two paths currently available to try out.

Killed both boss paths as NIN, THF, SMN, SCH with nary a sweat.