I've been trying to pull Soulfire from my deck entirely. The best replacements for it are PO and Shadowflame. Have you tried this yet? Thoughts?
I have a soft spot in my heart for Voidcaller, Floating Watcher and Demonheart because of their synergies with the rest of the shadowflame deck, but I've struggled finding which cards to remove for them. Dark Iron Dwarf is easy to remove, but putting all of them in tends to weaken the Knife Juggler and Undertaker synergies. I wonder if you wouldn't mind theory crafting about that?
Here's the deck I'm running atm:
2x Defender of Argus
The deck plays more mid-range than normal Zoo. The ideal is to have an Undertaker opening followed by a Knife Juggler boardcontrol phase and then a Demon-centric end-game.
The undertaker opening is the hardest bit to pull off because there's a possibility of mulliganing into a hand with 4 and 5 drops with this variation of Zoo, but with all those deathrattles I'm hesitant to remove Undertaker altogether.
In case you're curious: I find that I don't miss Soulfire at all, between PO, Demonheart and Shadowflame it's just not needed. Plus the discard is a bigger downside in a Voidcaller deck than it would be otherwise. Sense Demons is a blessing and a curse, it's great for Voidcaller and making sure I get my end-game, but I'm not sure yet if it's worth the dip in tempo.
Really my biggest complaint so far is the Undertaker opening. Loothoarder is an underwhelming component of the opening, but Clockwork and Leper Gnomes don't feel right either. If I took out Undertaker altogether, that'd open things up for shit like Flame Imp, Annoy-o-Tron, Argent Squire, Ironbeak Owl, or maybe even a Mech Warper opening with Spider Tanks and the like. Undertaker and his deathrattles take up so much of the deck that removing him would really open up a ton of options....
Sorry for rambling. Looking forward to your comments.