So here's the current version of my Sisters/Orchard deck: http://tappedout.net/mtg-decks/smallpox-blanket/
It's gone through maybe 5-6 significant changes since I posted the thread the other day. I ended up going Abzan so that I could experiment with some extra stuff, get my hands on Sylvan Scrying, and sideboard Abrupt Decay (since Blood Moon destroys my deck so hard lol). I reigned that in at this point, but I did keep a splash of green for Sylvan Scrying. Card is just plain better than Expedition Map IMO. Paying 1 to get Map on the board doesn't buy me any advantage since Scrying and Map are both 2CMC to tutor, and mid game I was blowing 3 mana to play and crack map on the same turn too often.
I also took out Dark Confidant for the moment, and this is something that maybe people could help me out with. I feel as if Bob would be fantastic in a deck with the same curve as mine, but with more disruption. As it is, I don't really have anything to help me interact main board while he does his thing...and he actually takes several turns to generate card advantage. I've currently swapped for Night's Whisper, which seems significantly weaker as a card, but which actually generates advantage more quickly for a drawback that's often less significant in a Sisters context. Am I an idiot? I'd be interested in hearing thoughts on how I could more effectively dig with this deck.
I've also added a few copies of Genesis Chamber. I'd added it...removed it...a couple of times in the last few days, but I'm currently thinking that it's pretty useful as a way of balancing out situations where I don't draw Illness in the Ranks. Zealous Persecution gives me double synergy here, because it not only kills Orchard tokens (when I can't find an Illness), but it also kills opponent Genesis Chamber tokens and buffs my own while promoting the interactions with the Sisters/Blood Artist/Priest that I want to foreground.
This is by no means a final version for the deck, but if anyone has some suggestions about what to explore next it'd be much appreciated.