Sacrificing creatures is a bigger tactic in the deck than the number of listed cards might imply. Avacyn’s transformation can be utilised in a few different ways but it relies on the death of a non-Angel creature. The ability to sacrifice creatures provides control over the transformation.
The ability is preferably instant and without a mana cost, like with the Remorseful Cleric, but cost is justifiable for additional utility of Cathar Commando and Restoration Specialist. Mortarpod fits well into this deck because it can be tutored as an artifact Equipment, and it can synergise with cards like Basilisk Collar for additional effects.
Daretti, Scrap Savant
Remember the Fallen
Graveyard recursion is limited to a small number of cards, but it is useful to have some recursion options because the deck discards cards to draw cards. Daretti can also sacrifice artifact creatures, and the Restoration Specialist sacrifices herself to bring cards back from the graveyard.