Healing in Arkham has historically not really had a good track record, and as a whole I try to avoid putting much of it in my deck as I can. This was a card that I thought maybe might actually finally give healing more value, if not as a universal thing then at least for investigators like Carolyn and Vincent. Unfortunately, while I do think the card can be an effective option, it's mostly due to one specific interaction and not because it's an overall valuable card.
First off, this card costs 6 XP. It is a permanent so it's something that will always be in play, but as a reminder Stick to the Plan as well as taboo'd Higher Education and Streetwise also cost 6 XP. You can also get any 2 card combination of Charisma, Relic Hunter, Another Day, Another Dollar, or Studious for that much XP. Soul Sanctification is a sizable investment of XP, so the rewards of the card are going to have to be on the same level as the cards I've listed as well as other options to be "worth it."
The big problem though is that generally speaking, you should be using your healing on investigators and allies that ACTUALLY NEED the healing, rather than investigators that are already close to full. Healing cards that are already perfectly healthy does nothing by itself, and IMO getting a handful of personal Unexpected Courages is really not a significant enough payoff to spend an action healing people over the alternative of healing damaged cards.
The card IMO really is only great if you have a useful effect that can overheal without having to really invest significantly in making it happen. One example of this is Surgical Kit. If you already have full Sanity and don't need to heal damage on the person you're healing, you can use a supply to draw a card and get a Soul Sanctification offering. It's not exactly the most insane payoff ever, but it's a nice option to have.
The other big card, and the one card that I think makes Soul Sanctification worth considering, is Fickle Fortune when you're playing with 3 or especially 4 players. If you find the card in your mulligan in 4 player, it gives you 24 offerings on Soul Sanctification minus one for each trauma (and it insures that every investigator starts with full health unless they're REALLY banged up) which with moderation will easily last you an entire scenario. Not only that, but you also get to trigger Vincent Lee and Carolyn Fern's investigator abilities on every teammate right off the bat. This can be extremely effective, especially if you pair it with Girish Kadakia and can help insure you're +4 on basically every test you care about. The big downsides are firstly that it costs 12 XP. I think it's still worth it in Vincent and Carolyn, but I think it might be too expensive for everyone else unless you're a Survivor with nothing else to spend XP on. The second one is the doom, but IMO this isn't that big a deal firstly because it lets one player have very effective actions all game, so the tempo loss early will be made up for as the game goes on. And secondly, if you draw the second Fickle Fortune you can use it to remove the doom and use your healing to keep your teammates safe which retroactively undoes the doom you added earlier.
One last effect that I didn't mention is that Soul Sanctification makes it so overhealing still counts as healing, which is important for Vincent and Carolyn as it means you can still get your triggers on fully healthy cards. While this by itself might not be worth 6XP, it's a nice QOL boost that can help a bit. However, it doesn't trigger on allies which can be annoying if you got a Girish in play as you can't use him at full health/sanity to get charges.
Overall, I think this card is good in Carolyn and Vincent at higher player counts in combination with Fickle Fortune, and really not anywhere else. As mentioned before this card costs too much XP and is too inefficient to normally trigger for it to be useful outside of its combo with Fickle Fortune. But that combo is powerful enough and has good enough synergies with the healing investigators that I think it's worth considering at higher player counts.