The recent addition is sub-optimal for an average/new player; as it currently stands out, a new player wouldn’t know that such a powerful tool is locked behind a side-quest at Whitesummit, despite being told that there’s a new quest available once they reach the awakening.
Thus, we can make use of Rill Hendrix’s (canonical) sensing ability to make some sense and include him and his quest in the Storyline.
Chapter 5, Part 12: Return to Wind-Row
After you obtain your first Awakening, there is a ‘supposed’ power surge that is sensed by Rill Hendrix (and possibly other characters, but for the sake of this quest and given how Rill Hendrix is, again, supposedly adept at Sensing given his years training it and the whole Aberration dialogue, he should be the only one that can reach us quickly enough, which can be seen as plot convenience, but the card of “assassins are fast” can be pulled somehow), and given how this power surge ‘lasts’ for a while, he senses us and an encounter with him ensues.
Chapter 5, Part 13: The Former Assassin (NEW)
Rill Hendrix is faster than us and reaches Wind-Row Island via something we’ll call “plot convenience”; after that happens, we find him talking to Warren, he has a respectful yet friendly tone towards Warren, implying that they knew each other (given that the Assassin Syndicate encompasses the whole War Seas and how Warren was at the Stepstones earlier in the Storyline, we could push for something about him going to Rill Hendrix to ask about the Order).
He notices us, and speaks about the whole power surge and how he had to check if it would have been a threat to Whitesummit/Blackwater Grotto, but seeing how Warren is with us, he understands that we pose no threat to the Blackwater Grotto and that we must have bigger matters to be concerned about.
Later on, he voices his concerns about the rampant corruption that has been growing in the Assassin Syndicate, and on Warren’s request about us needing more strength, he offers to train the whole group to train what is known as “reflexes” seeing how most of us (except Neviro since he’s not powerful enough 
) have reached the strength necessary to make said ability ours.
The standard quest, now included in the Storyline, begins, and at the end of the quest, we are told about dodge reflexes just like in the quest.
Once everything is done, he bids farewell to us and Warren, stating how we must be careful of the Assassin Syndicate and how there must be something going on aside from the usual activities.
Conclusion
This should possibly make enough sense to be considered; and while it is true that Rill Hendrix never leaves Whitesummit, it can be considered plausible that he’d at least go to check if something is a threat to axe it down pre-emptively if the situation calls for it.