Well, maybe CCP did a stealth change when they redid the character sheet standings section.
Back when I was doing a lot of missions while working on ‘The Plan’, it seemed that a majority of the Storyline mission offers were opposite to the Agent Division you were working prior to receiving the Storyline offer. Meaning if doing Distribution missions, the Storyline offer would be a Security mission and vice versa. It also seemed that Mining Division would give various Storyline mission offers from all divisions.
It’s been a long time since I’ve done a lot of mission grinding, I don’t remember if it only pertained to the 16th mission or if all 16 missions needed to be done by a different Agent Division.
Basically would have to run a couple of tests, the first with the Storyline Agent belonging to the same Division as the Regular Agents.
Run 16 missions for a specific Agent Division and see what type of Storyline offer is received, then do the same thing again but run the 16th mission for an opposite Division.
Then run the same test again with a Storyline Agent from a different Division. Course the game always picks the nearest Storyline Agent so doing these tests will require some research and travel to complete, much like how players get the Storyline Agent to be in the same Corporation as the regular Agents they’re running.