Agreed. In my current game, I have a character with magic sponsored by Eris, and the magic covers good luck or bad.
I mean, if you think about it, quite often bad luck for you is just good luck for someone else, and vice versa.
That in mind, having some kind of balancing act as an aspect of it would be appropriate, too -- sure, you used your entropomancy to get a winning lottery ticket, but maybe next week your car is wrecked in a freak accident.