This card looks to be the absolute king of damage and horror soak provided you can reliably find at least the second copy. It compares favourably to Elder Sign Amulet with regards to horror soak, although it'll set you back a bit more experience, and it makes Armor of Ardennes look like a complete joke. What's more is that Spiritual Resolve doesn't hog the ally slot, unlike Survivor soak champions Peter Sylvestre and Jessica Hyde, and a single Arcane slot is unlikely to dissaude Guardians who so far only really want the second slot for Enchanted Blade and its upgrade.
One very nice thing about spending a 5xp chunk on a Myriad card is that you get three copies of it so you will rarely ever completely miss drawing what you spent your precious experience on. This saves the frustrating experiencing of kitting your investigator out with a big new toy only to feel like that was completely wasted experience when your power weapon doesn't show up for most of the scenario.
So, who wants to live forever? How many Guardians actually want to sink 5xp and three deck slots into nothing but soak? Roland Banks appreciates some sanity padding to mitigate trauma caused by Cover Up, but he rarely wants for damage soak, so he's probably better off looking elsewhere. Tommy Muldoon prefers to defeat his soak cards in order to trigger his reaction, and his card pool affords him many less experience-intensive choices. As for Carolyn Fern, while she can take Spiritual Resolve due to it healing its own horror, her reaction ability only pays for healing investigators and Ally assets, so she really has better things to be doing.
Really, Spiritual Resolve is so far solidly a Mark Harrigan card. Mark needs both damage and horror soak/healing to make up for the direct damage from Sophie and his pitiful sanity, and furthermore the extra cards drawn by his reaction make it likely you'll find multiple copies of Spiritual Resolve to take advantage of its free triggered ability to efficiently heal it. Some Mark lists already play Smoking Pipe to draw cards while keeping the soldier sane; with Spiritual Resolve, both the pipe and Painkillers become more attractive in allowing you to move damage and horror onto this easily healed ritual. Alternatively, Solemn Vow lets Spiritual Resolve protect other investigators too.
Hopefully in the future there will be a couple more investigators for whom Spiritual resolve is a desirable card worthy of its experience cost. With all the Guardian cards that encourage you to tank attacks and generally suffer on behalf of your team its also possible that this card is intended to fit into that archetype as well, but I think we're yet to see an investigator who fully rewards that playstyle - or at least yet to see one with access to this card. I omitted Zoey Samaras earlier, but I guess she'd be the current natural fit for such an archetype given her high willpower, her deep health and sanity pools, and her reaction paying dividends for enaging everything.