I'm would prefer to keep Holy as it is, however the change is open to discussion. Here is my suggestion:
Basic gain 25, bonus gain 5, Holy song - gain random resources based on played card rarity (Common - 1, Uncommon - 2, Rare - 5). Replace highest rarity Undead card from opponent's hand with Purified ashes. Can only replace a card with same or lower rarity as was the played card.
Changes:
- stock gain is replaced with resource gain, but it's triggered regardless of the discard effect
- discard effect remains the same