Including too many cards like this in your deck makes you vulnerable to mass removal effects but this is easy enough to compensate for
Slides down just a little bit due to the low density of threats
Delete is also a solid way to deal with a ton of creatures and make sure Missy sticks around since you can control how much damage is dealt to all creatures
With very little setup on the board, you can create loops to continuously return creatures like Hangarback Walker back to play by sacrificing it to Ashnod's Altar for infinite mana and dies triggers
Also, as you might expect, proliferating your opponents' poison counters is a strong strategy for winning games, and cards like Inexorable Tide or Contagion Engine are effective ways to achieve this
This, in turn, pushes prices up, as the expected value and hype around them increases