[AaronBrown]

The main reason to look at standard deviation is to figure bankroll requirements. Another use it to know how long you should put up with a downswing before deciding that you have to change your game. There's probably some subtle way to use it per starting hand, but nothing springs to mind.

Variance is not useful directly, only its square root, standard deviation. You could figure it per hand, but it's more commonly stated per 100 hands or per hour.