Instead of deleting an existing Druid deck I removed all cards and then rebuilt the deck with different cards. Upon playing a game with the new deck, the old list of cards was used. Upon returning to deck manager the old list was also showing in the deck.
My exact series of operations was playing a game with the druid deck. From the Play Wild menu I clicked My Collection. Here I access the deck in question and manually removed all cards to rebuild the list with different ones. I clicked Done and then Back returning to the Play Wild menu. I started a ranked wild game with the Druid deck and the old list of cards was loaded.