The longer you look at this card, the better it gets.

Say you're running this as a having option for your bruiser oriented survivor. Ru ln6 0 ok l

A single action 6 heal per investigator is huge and unrivaled by any card. Sure, you have to drop a doom. But I would challenge you and figure out any other way to heal 3 damage/3 horror from your investigator in under 3 actions. The doom also does not auto advance, so you can get lucky and suffer no downsides for this at all if you get a witching hour draw.

Then comes the other use for the card... taking mild damage and horror to push the clock back one. As long as you have another healing ability (like Spirit of Humanity) this is an outrageously overpowered option. Compare it to other cards (like Golden Pocket Watch) which require you to draw, play and pay for it, this only requires a draw, for five less experience.

Overall this is a very powerful card with a great amount of flexibility and very few downsides.

In solo it wasn't bad to include a couple of these in a deck for Rita Young and the like, even though she can't really recur it outside of Resourceful etc. But with the advent of Crafty, I can see an argument being made for having this in hand as a starting supplemental 'weapon' by some survivors even in multiplayer. I'm using it with Rita Young in a 3-player right now, and having 1 Crafty - or even better, 2 - to both pay for the play of this card and amp up your Fight to as high as +6 means you can take out monsters with that little bit extra. Even the Clover Club Pit Boss can be a challenge if you're Rita as main monster manager. Elite so can't Waylay, so use a Cheap Shot for 2 damage and you've got 2 left to go. Fighting 3 on 3 doesn't set the world on fire. But use the Gravedigger's Shovel with Crafty and you can rock out two actions of 3+2+1 = 6 v 3, beating the Cultist on Standard.
Not the best weapon, but still a fun one when Rita can deal 1 Damage with a standard evade and a very reliable 1 Damage with the Shovel.

What makes heal decks more viable now is not cards such as Soul Sanctification but Vincent Lee the investigator's deckbuilding options. Because he can use any cards 0-5 that can heal, he has a wide and versatile library of deckbuilding options that was hitherto unavaiable for any investigator. Runic Axe becomes monstrous with him, and he can be a very effective fighter even as a primary cluever.

What gimps this card for me is that it only applies to excess heals for investigators, not allies. There are actually less cards in the game that heal investigators specifically rather than allies. I know another reviewer mentioned a combo with Daisy involving Earthly Serenity. However, I don't think Daisy wants to spend her time building up a stockpile of Unexpected Courages that she can use twice per test. As a Seeker with an investigator ability that synergizes with Tomes, she has a lot more interesting and powerful options than spending time with Earthly Serenity. The build is viable, but it doesn't sound optimal and more of a way to utilize a new and fiddly card.

What makes heal decks more viable now is not this card but Vincent Lee the investigator's deckbuilding options. Because he can use any cards 0-5 that can heal, he has a wide and versatile library of deckbuilding options. Runic Axe becomes monstrous with him, and he can be a very effective fighter even as a primary cluever.

arkhamdb.com

Overpowered in a Vincent Lee recursion deck with the combo piece Bandages + Well-Maintained + Spirit of Humanity. Endless recursion of Bandages, fill the bag up with 10 Blessed Tokens with Spirit of Humanity. This also procs Vincent's ability, giving you endless On the Mend (Unexpected Courage). You'll need someway to offset the horror damage, though.