Interesting and powerful card, that is released in the same box as the upgrade of Sign Magick, for the same amount of Experience, and the same resource cost.
Nevertheless, I will prefer Sign Magick to The Hierophant • V for the Fast Aspect, to keep the Tarot slot free for Four of Cups, and most importantly for a free trigger of another spell: You killed an enemy (or not btw), get a free investigation (without AoO); you didn't kill the enemy, get an extra attack or an evade to dodge the damages.
Replacing Four of Cups for The Hierophant • V to have an extra slot to play Holy Rosary is the same as paying 2 XP and 2 resources for 2 Sanity. (Mr. Pawterson is looking at you). Crystal Pendulum and St. Hubert's Key are barely better in that slot.
You're therefore more likely to use this card to improve the size of your Arcane pool.
Is it the best card in doing so?
I don't think so. Familiar Spirit and Sign Magick (0) are lvl 0 cards, and Sign Magick (3) offers insane options for the same amount of XP and using a slot that is less contested in Mystics than other classes.