This one seems to be a very interesting card for Guardians since defeating enemies is basically what they do, but this card has a catch to it. Of current guardians, all but Carolyn Fern are able to take this card. A pity for Carolyn Fern, since it is the bonded card, not this card that heals horror.
For Leo, Mark and Roland this card has to compete with the always powerful Police Badge and the potential Police Badge/Well Prepared combo with one additional icon compared to this card. It also has to compete with the strong Hallowed Mirror. While also healing, the Hallowed Mirror does not cancel an icon from the chaos bag but does not need charges and does not cost any xp, so I think I would prefer the Hallowed Mirror over this card because of this. With Zoey Samaras, this card competes with one of the strongest investigator-specific cards in the game which is of course Zoey's Cross with an obvious outcome.
Of non guardian investigators Ursula is able to take this card currently (Father Mateo can take blessed only up to level 3), but she is very bad at defeating enemies with her 1 so she is not the obvious investigator to charge this card.
There is just one investigator I think of, when looking at this card, and this is (it might be a big suprise so tension is rising): Akachi Onyele - she can take "uses: charges" cards up to level 4. She does not really require the Holy Rosary because of her powerful stat and she definitly is able to kill monsters and she really like cancellation of special symbols for her spells and she starts this card with 1 charge and also can charge it with tokens. Akachi Onyele is a very potent monster slayer for a non Guardian so it might be worth a shot.
As a conclusion the most obvious investigator for this lv. 4 guardian card might be: A Mystic.