Yeah, the actual feat says that it's against a flanked target. Since you can't flank with one person, or flank at range, this means two people flanking the target and you firing at the target from range.
For example, the classic party is Fighter, Cleric, Wizard and Rogue (perhaps an archer ranger too). So who's going to flank? Now, the above mentioned beastmaster might be a good person to have around to help you with this. Barring that though (or multiple Rogues/Defenders/Melee Cleric), it's probably going to be a rather situational ability.