I refresh the game for any fight that takes longer then 20 seconds. Lab bosses, story mode bosses, arena fights, baal/cerb fights, pirate ship fights. All rewards are determined the moment you engage an enemy so choosing a card is a pointless exercise.
The only reason I ever 'watch' a fight is if I need to improve my chances at winning. All the time spent watching fights you could be afk and training or doing more fights.

Everyone knows it, everyone does it.