For investigators who have access to Mystic (5) or Spell (5), it's hard to find a good reason to upgrade to Spectral Razor (2), Read the Signs (2) and Ethereal Slip.
A single-use event or skill must be stronger than assets that can be used multiple times to be worth including in your deck. The level 0 version of these events compare very favorably to Shrivelling (0) or Rite of Seeking (0), giving you an efficient way of dispatching with 3hp or aloof non-elite enemies, or to reach higher skill test values.
However, once you have some XP in your deck, these level 2 version compare poorly to the likes of Brand of Cthugha (4) or Rite of Seeking (4). They deal 1 less damage to elites and get 1 less clue. They're significantly more expensive than playing spell assets. They require other support cards in play before they can be used*. They can't be used multiple times per turn - if you fail a fight check you're just out of luck.
Alternative explanation using Gru's plan:
- Set up Prophetic and Olive Mcbride (2), have Read the Signs (2) in hand.
- Play Read the Signs for free using Prophetic, using Olive Mcbride during the skill test to guarantee a symbol draw and recur Read the Signs to your hand at the end of the round.
- Discover 1 less clue per round than Rite of Seeking.
- Discover 1 less clue per round than Rite of Seeking?
So, why would you take these cards? You take them because you're playing blurse and you want your arcane slots for other uses**, and/or because you don't have access to mystic 4. Kōhaku Narukami is the poster boy here, with strong economy and the being able to take advantage of the extra arcane slots.
Also, these cards are a dark horse on off-class mystics. Anyone who can take these upgraded events can also take Olive McBride, Rod of Carnamagos***, and Robes of Endless Night. Bring your own blurse generation and you have a party going.
Sister Mary gets a much needed buff with XP here, allowing her to properly flex into investigating in ways she couldn't before. She has natural symbol generation, Prophetic access, and can discount repeated plays with Rite of Sanctification. She also often runs other cards that benefit from token manipulation like Blessed Blade or .35 Winchester.
Sefina Rousseau likewise likes these events even though The Painted World doesn't interact properly with the return-to-hand effect. These events are some of the highest action-compression she can get at the time of writing, and competes very favorably with the Rogue events of the same type like Pilfer and Backstab. Rogue access also gives her cool toys like Double, Double, extra actions, the economy to support repeated plays, and lets her double-dip on the stat bonuses from Geas and The Black Fan.
//Front Daisy has better things to do in general, but can run them as a jank deck of sorts, since seeker does have good curse generation and gets acceptable mileage out of curses with Prismatic Spectacles and Gabriel Carillo.
* unless you have to discard the card after use, but why would you do that after paying 2xp for it unless you have no choice?
** e.g. for Spirit of Humanity or Close the Circle
*** despite much hand-wringing about how unintuitive the interaction is, the Rod feels obviously designed to combo with these set of cards