Black Devotion /w Green. Needs help! (Standard)

Hey everyone :3 I need advice on this deck. I've played it at FNM and against a couple of friends (and my own) standard decks and it seems pretty strong. I went 3-1 my first time playing and lost (utterly) to an esper control deck. Since then I have reworked it a bit and am hoping to stand a chance.
I need advice on cards to add/how to beat esper.
Much thanks :D

Strategy of the deck is the same as black devotion; it has a good list of answers and can shift from control to aggro in different match ups. Noteable additions are

Varolz, the scar striped: Varolz is nice for the scavenge function. I can turn him into an 8/8 regenerate with a demon in the graveyard, turn a lifebane into a 9/7 intimidate, or make a large flier. Good synergy with pack rat's ability to pitch a card. Negative synergy with deathrite, but I generally use deathrite on instants and sorceries

Deathrite Shaman: A strong flexible one drop for the deck. Sided out in a lot of match ups, but good against control. Really strong against the mirror match or other black devotion decks.

Herald of Torment: Considering using more of him than lifebane for a more midrange-y feel. Really good for ending games with Varolz. Can instantly turn something big, into something bigger with flying. Also adds 3 devotion, improving the power of the merchant. A solid three drop.

Golgari Charm: Another card that often gets sideboarded. Really good against mono-blue, white-tokens, and board wipes. Also has good spot enchantment removal which helps against detention sphere. Overall useful, but only in some situations

Abrupt Decay: Possibly the best, and only, removal I use against Esper Control. Removes detention sphere and can't be countered. Good against aggro and likes to shut down mana ramp.

Vraska the Unseen: Really up in the air about her. If she resolves on a control board, she can dominate. She also has decent protection against aggro (can mass wipe their units) and usable as a murder against midrange. Her final ability has won me a couple of games, but her 5 mana cost really hurts.

Scavenging Ooze: Now this is just more or less a filler, however I think it could be useful against control or R/G monsters. I can pump him up for cheap using cards in my graveyard. Demands an answer from the control player

Mutavault: Nothing to really say here. 3 Mutavault stretches my mana-base a bit, but it's worth it for the aggro-beatdown + pack rat swarm. Considering dropping to two