I don't actually really want a solution to Caldara. Yes, she's potentially powerful. But that's why Caldara decks are so much more popular than they were before. I don't think abolishing a power deck type is necessarily a step forward for the game...
But if we have a solution, I'd prefer a card-based limit rather than a hero-based limit. I'm fine with resurrection cards removing themselves from the pool -- they're expensive cards that are unlikely to be recurred in the first place unless you're exploiting a discard ability, and limiting the discard ability immediately makes the hero worse. Companion decks can resurrect Caldara more easily but also dilute the impact of her effect.