
I think an overlooked use case for this card is in Daisy Walker. Her willpower isn't that great, and it isn't often worth using spells that don't boost , and the ones that do boost it are too high level for her. She's not too likely to use arcane slots aside from Arcane Enlightenment or some other niche cards.
Obviously she's never going to substitute , and she doesn't need to. And it seems at first that getting a boost of only 1 to (without extra damage) or isn't really worth 2 xp, 1-3 cards and both arcane slots, but the most important consideration is Higher Education. Since it's a permanent, this combination of cards can convert any test to something that can be astronomically boosted with only a little bit of money, something that's easy enough to come by as seeker, and cards in hand, which are also easy enough to come by in that class.
It's not something that lets you fight primarily, but it can finish off a weakened enemy, and it can let you evade when desperate. It's also good at dealing with the rarer or even treacheries.
Also worth a consideration are all the seeker cards that interact with secrets. Eldritch Sophist and Truth from Fiction let you keep it around even longer, and the former lets you move charges from it to stuff that's more useful as the situation calls for. With that in mind, the three copies can be extra easy and fast secret gain, for use with other great secret assets, of which a few have been teased for the Innsmouth cycle. Though some of them also compete for arcane slots, Daisy can run Familiar Spirit in a pinch, or just run the very best slotless or Tome assets that use secrets. Old Book of Lore is a particular standout.
Overall, it isn't really necessary, or something that seekers don't have tools for already. However, most of these tools are events, and having something permanent - secret supply notwithstanding - on standby for turns where Mind Over Matter would feel like a waste is pretty good.