A 4/4 Zombie Wizard for four mana, Varina can allow you to quickly cycle through your deck, as whenever its controller attacks with one or more Zombies, they can draw and discard that many cards, even gaining that much life in the process
For Hearthhull, I think it comes down to the fact that this deck is dumping tons of lands into the graveyard and it most likely wins the game by bringing them all back in one go - using a card like Splendid Reclamation - for a mass of triggers
Withering Torment Suggested Cut: Feed the Swarm Even if youre playing a normal game of Commander, this deck has a tendency to become the archenemy at some point during the game as other players become concerned about their dwindling life totals
So long as it doesnt get reprinted, however, itll definitely be a card to watch going forward
Alternative costs, additional costs, and cost reductions don't change a spell's mana value