We've all known for awhile that RNG and COR need a little boost, when it comes to how on par they are with other Jobs at the moment. But what could also help encourage people to bring them along, would be the addition of Enemies/Bosses that require and/or are highly susceptible to Ranged Attacks.
IMO. They should add more mobs that can periodically fly and attack from a distance. Especially when it comes to bosses. OR... Go into "semi-flying" mode and become resistant to melee damage, and highly susceptible to Ranged Attacks. Sort of making the phasing in and out of flying less one sided.
This in turn would increase the want/need for Ranged Attacking jobs, such as RNG, COR and... Shuriken NIN's! (Please refer to NINJA JOB forums "A Ninja without Throwing"... lol).
But yea... All in all, this is where I see the major key in reviving Ranged Attackers.