I can see an argument for having it be S-Tier (the ability to sacrifice a creature for free to draw a card is super powerful, potentially enough for it to show up in multiple decks) or even B-Tier (while various Sacrifice decks seem like the most obvious home, it's possible that the lists are so tight that it will be hard to find room for Yawgmoth, Thran Physician)
From a story-crafting/game-design vantage point, Hunted Witness is a thing of beauty
Jin-Gitaxias, Core Augur has flash and gives Jodah's player a massive advantage in cards, and Sheoldred can force sacrifice while reanimating friendly creatures
It also has access to bounce spells like Into The Flood Maw, which can bounce an Agatha's Soul Cauldron after it exiles Vivi to permanently get rid of that Vivi copy
The Blight Curse and Dance of the Elements Commander decks, along with the rest of Lorwyn Eclipsed , are available for preorder now from your local game store, Amazon, TCGplayer, and elsewhere Magic is sold.