This is, I think, a bug introduced when they extended the storyarcs for Stephanie Peebles and Long Jack's range from 20-24 to 20-25 (which I believe was done to make organization of the Ouroboros listings a bit more consistent, so that the Striga arcs are all contained in the 25-30 subsection).
There's two criteria for the contacts in Striga Isle to introduce you to the next one in the chain:
1) You've filled the reputation bar with them to 100% by doing their missions.
--OR--
2) You outlevel them, whereupon they're automatically introduce you to the next contact regardless of your reputation status with them.
Here's the bug:
There is one mission from every Striga contact that is a 'hunt (x) mobs in (zone location)' that is not actually part of the storyarc itself, AND was not bumped up to be in the level 20-25 range like the contact's storyarc's. This is a mission you'd always get before actually starting the arc, and it counts towards getting the contact's reputation status to 100%.
So, in the specific edge case of a character starting Long Jack at level 25 means they'll never get that first hunt mission, and their rep bar will never be 100% full, which ultimately means they won't get introduced to the next tier of contacts until the game sees they've outleveled Long Jack (when they hit level 26) which makes them automatically introduce Tobias.
The workaround (so to speak) that I found was to just speedrun Long Jack's arc in Oroboros, then when I finished his arc and called it in, the rep I built up in flashback for him was added to his rep bar in my 'inactive' contact list (a change they did ages ago, I couldn't tell you when), and while I was still level 25, the game saw that I was at full rep with him and he introduced me to Tobias.
