My opinion on the SP aspect of this is that I think they are about to die out. Gyarados overpowers and outspeeds it, Vilegar is just too much of a hassle for it with the trainer lock, and Machamp is too hard to get ahead of in prizes. Also, if Nidoking becomes popular, that would ruin Luxchomp.
Honestly, I would feel safer bringing a Lugia Legend deck to cities than Luxchomp.