How about running whip of erebos?

for me I would honestly take out Erebos, God of the Dead for Pharika, God of Affliction. You'll still be able to gain the indestructibility via her, and her have a better way to ward off your opponents through snake tokens. Gives you a little more synergy with that since you're not always able to get Soulflayer out. As for Commune with the Gods vs Dark Deal it's up to you. Dark Deal is a pure and utter gamble, but I rather enjoy gambling on games for fun. I personally run an izzet control/burn with Riddle of Lightning MB and hope to scry for a Dig Through Time or Treasure Cruise but that's just me. If you want consist draws and ways to work through to your combo, i'd stick with Commune with the Gods. Hope this helps your deck out a bit. :)

also one more thing, you have a bit of redundant removals in your main and side. Bile Blight is mainly used for tokens first and foremost beyond any other target. Silumgar, the Drifting Death can do just that very easily. He essentially is a more constant version of Doomwake Giant. I'd drop Bile Blight keep Drown in Sorrow and figure our what to place in there. Possible a Crux of Fate? For those extra long mid-range games. Just a thought.