It's O'Brien and Garak in a murder mystery without the mystery. (Actually, it evolves into DS9s version of "The Most Dangerous Game"). This horror episode, pairing up the two characters for the first time, takes place on a mostly abandoned sister station, giving the episode and the show a new setting at no expense. (Here's a secret: the sets for the sister station are actually the regular DS9 sets with new lighting! Don't tell anyone). Star Trek, going back to "The Man Trap," has often struggled with horror stories, but director Mike Vejar is up to the task here, handling the timing with expertise. The episode builds its suspense nicely before delivering "jump" moments at just the right times. Meanwhile, having a sister station not only saves money but story time. There's no need to orient the viewer to the new setting. We know the Promenade is the Promenade and Ops is Ops.
Is Empok Nor a Top Ten episode? Of course not. It's a low-budget filler episode that doesn't lend itself well to repeat viewings. (Nobody would argue that this is either the best O'Brien episode or the best Garak But does it succeed at what it sets out to do? Absolutely.