How does this card stand on it's own?
On it's own, and undamaged, you are gonna have some problems simply because it's first attack relies on having alot of dark pokemon out and it's second attack needs Zoroark to be hurt. Brutal Bash does twenty times the number of Dark Pokemon you have in play. This attack with a full Dark bench can be very dangerous (anywhere from 20 (40 with two special darks) to 120 (140 with special darks. Dark Rush is horrrible if Zoroark is untouched, but as a last resort attack (i.e. more than six damage counters) it becomes a bad grass capable of doing some heavy damage, especially if the two dark energy on it are special darks. The weakness of this card won't really be a problem seeing as the only fighting pokemon in the meta is Terrakion. The resistance will be fun against Mewtwo EX, the only Psychic pokemon in the meta right now, since Chandyplume has gotten a bit slow and out of date, but even then, Chandy is weak to Zoroark and the fact that, if the Confusion and Burn don't work, you're kinda screwed. The retreat, not that bad, but not that good.
2. What cards, if any, does this card combo with?
Darkness Claw and Special Dark energy are going to make this card very evil. You can easily do 200+ damage with Dark Rush. And with the Large Cloak from Dragon Blade, you can do up to 280 damage, 280 DAMAGE! That is just, mean. Brutal Bash, with a Darkness Claw and four Special Darks can do 180, OHKOing any EX...without Eviolite. And with Darkrai, hey look, free retreat.
3. What role does/could this card have in the metagame?
This card could easily bring back Darkness Pokemon. I think that there could be an amazing deck with Zoroark, Darkrai EX and maybe the Mandibuzz from Black and White (Heavy damage to Stage 2's) could make a pretty good Dark deck. I'd have to do some testing with this deck to find out where it stacks up, but I think it could be a Tier 1.5 or 2 deck.
4. Pokemon Rating:
This card is amazing, and with the amount of Dark pokemon and trainers in this set to back it up, it will be even better, so for the attacks, weakness, resistance and HP, I'd give it a 9/10. The card print has pretty great detailing and the darkness fits perfect with the Dark Explorers set so, 8.5/10. So overall, 8.75-9 out of 10 seems about right.