Do you dust other characters cards to make one really strong deck?
That is to say for example that you want the best possible Rogue deck do you then dust all other epic and legendary cards from Druid to achieve this?
I dust cards with building a ‘really strong deck’ being the intention. It’s yet to work out that way though 
there is no one deck that is worth it to dust all cards from another class. and even if there would be, it likely wouldn’t be good enough after the next expansion anymore, so this plan is a really bad one.