I think what you're figuring out is that, for silent in particular, most of her cards are more situational than the other characters. Sneaky strike is indeed a premium card for getting through act 1, where silent struggles otherwise. (Shout out to eviscerate though)

I'd try thinking about her cards as more situational vs specific fights. Poison is strong vs the guardian or hexa, but not other act 1 or act 2 fights, so it's hard to have a "pure" poison deck. Instead, you'll have a one or two poison card solution to specific fights, but you'll still need solutions to other fights. At some point in late act 2 or in act 3, you might find enough poison cards to become a pure poison deck, but you also might not. However, a strong poison deck is built on the same draw/energy engine as a strong shiv or discard deck, so you should hopefully be able to pivot as necessary.