With solid offensive stats, boosting moves, and a handy speed that puts it before the monkeys, Garchomp, and the base 100s, Zoroark looks like a pretty serviceable sweeper. Its ability is just plain awesome, though we don't know how it works or how to harness it.
You could use it to trap things with a bluff, or, for example, pretending to be something that lures a Shanderaa or other Ghost, then hitting it damn hard with a Dark-type STAB. If this is possible, Zoroark is a great Shanderaa check. However, it's also frail, and has a limited physical movepool. Furthermore, apart from Illusion, it's basically outclassed by the faster, stronger, and better-movepooled Darkrai.