I don't think it's fair to put down those who dropped RNG after the nerf. Ammo can become expensive if you aren't HQing it yourself, and paying all that money for mediocre damage is frustrating, regardless of how much you love the job.
I realize that a lot of RNGs will say they put out the highest DoT in many of their parties, as Aluus stated. I'm one of the guys that believes that if you're paying for your damage, it should be that way in EVERY party.
For example, I was XPing on my MNK the other night in Yuhtunga Jungle. We were 5/6 and looking for another DD, and someone mentioned their friend, a RNG, just started seeking. I was hesitant because I know the hit RNGs took, but invited them anyway.
By the end of the (somewhat brief - 18 mobs) party the RNG had put up 3123 in damage, which was 17.35% of the net damage. I had put up 6026 in damage, which was 33.48% of the net damage. Now, I paid a bit for my gear, but after the party is over I can sell my gear and get it all back. The RNG can't. It isn't right that the RNG dumps several nonrefundable thousands of gil into ammo and puts up HALF of what other melees are putting up. Maybe this RNG is a subpar representation of the RNG population, but would a more skilled RNG have put up twice as much damage? Who knows...?
Pre-nerf, a geared out MNK could outdamage a RNG with some work. From what I've parsed post-nerf, a completely geared out RNG has to bust his or her *** to keep up with or outdamage melees. Is this fair? A geared out and skilled MNK will outdamage a geared out and skilled RNG these days, even if he engages and goes to get a drink. The RNG can't do that.
RNG can put up great damage when they work hard, and so can DRG. I have great respect for all classes if they work hard. The problem is that parties sometimes aren't willing to take a risk and invite someone they don't know is hard-working. If they invite a DRG, he had better be one hard-working DRG to earn his keep, while if they invite a MNK or WAR/NIN or something of the like, maybe they don't have to work as hard. The same applies to RNG.