As long as you can put it into your graveyard, you can Debtors' Knell it out
It is rather on the all in side, not only because it hits your total resources pretty hard but because of the style of deck where Smallpox is optimal - if all your cards are cheap (or at least the ones you plan to cast) then you are less likely to have that much late game legs
In an ecosystem with Set Boosters and Draft Boosters, customers don't get the full experience
Cards that grant evasion make sure it connect, like Whispersilk Cloak or Rogue's Passage, while its built-in recursion ensures it comes back even after dying
Her clock is slow when solo and she is one of the most vulnerable cards on this list being fodder to most hard removal and wrath effects
In the games I lost, I felt like I might have had a chance if I had sideboarded a bit more carefully