This applies to both Dalaran Heist and Tombs of terror.
When starting a new run, you are presented with a choice of 4 different decks.
Picking any of these decks with always result in you being given the first option for the run.
This seems to apply across all classes and difficulties.
Example: warrior has the options of tough crowd, burning fury, boomin or a random deck. Selecting any of these with always give the tough crowd deck.
