i don't know if this has been mentioned, but besides spiritomb, you can use sableye. Zoroark can use nasty plot w/o revealing itself b/c most would believe it's a mischievous heart sableye. You can use substitute as well, although it probably be as efficient as using nasty plot. There are also other non-attacking moves both sableye and zoroark can learn. Sadly, once it attacks, the jig is up b/c zoroark will most likely attack first, something sableye can't do. at least, like spiritomb, the fighting weakness is hidden.