I would recommend Obzedat, Ghost Council . Swings for a bunch and dodges alot of the sorcery speed removal in standard right now(Especially in the Azorius control decks). If not main board, then maybe 2x in sideboard for the matchup mentioned above. I would also say that the Sin Collector Could probably work in the deck(Free pseudo duress stapled on a creature.) You could probably take out 2x underworld connections, though if you feel 4 works, then it probably does. Overall, the deck looks solid.

Sin Collector is a card I'm testing in my sideboard at the moment in place of Duress . I honestly like it a lot - it feels very relevant especially with Gift of Immortality .

Obzedat, Ghost Council was an easier consideration, I feel Blood Baron of Vizkopa is strictly better. Pro Black/White feels very relevant in the current format to me and a blocked lifelink is an equal health swing - a direct attack is double.

I'm also leaning towards taking out Blind Obedience in place of Erebos, God of the Dead just to better deal with anything with lifegain. I know how brutal Erebos can be vs this deck and I'd like to be able to pay in kind.

Id recommend taking out one of your merchants, since he's so expensive. Also because you already have so much other life gain stuff. Also, I'd recommend adding at least two Vizkopa Guildmage to your main board, since she could turn all your lifegain into damage near the end game. On another note, if you want more cheap life-linkers/extorters besides Tithe Drinker then I'd consider Daggerdrome Imp and Basilica Screecher .

On a completely different note, if you want some monetarily cheaper removal cards, I'd recommend Executioner's Swing and Ultimate Price .

Only sideboard one Erebos. They are good conditionally, but your devotion isn't quite high enough to play him effectively. His card draw ablility can be duplicated through Underworld Connections . Run your Thoughtseize and Sin Collector Mainboard, as they usually are effective. In their empty sideboard slots, put Dark Betrayal and Doom Blade . Ultimate Price is a good option against most devotion decks, as you can get rid of stuff such as Polukranos, World Eater , Desecration Demon and Master of Waves . I would reccommend more Blood Barons, as they can race with Reaper of the Wilds and Stormbreath Dragon . An Elspeth would also be a good option.