This gameplay “mode” is just a total waste of precious time, at least for me. It makes no difference whether you actually manage once in a hundred times to manage a good deck, you can never win enough of Arena play so that the award is worth the game time. The programming places you against decks/players that simply cannot be won. And this disturbs me the most. Why can´t the “lottery” place you against decks that are equally good? For example today I played against a hunter deck that had like 6 units on the board in about 4 rounds and all of mine destroyed. From there where do you think my chances were? Close the arena or reprogram it for heaven´s sakes! The worst mode of the game and the most unfair one.
ProTip: You can shut down Arena any time you want. The secret is to not press the Arena selection button.