The main argument I see is that leveling through other means does not make you know your class better; this is something I want to argue. If they made dungeoning the primary way to get exp, people would learn their jobs better at lower levels. Sure, there are people that get carried through storyline dungeons, but if you had to use PUGs to primarily level? That'd be a different story. It'd force the DPS players who insist on pulling, healers that over heal, and tanks who try to pull with Flash, quickly learn the correct way to play (or suffer many, many wipes).
While doing the level 47 Molboro quest is a good 130k exp per run (and really fast/easy for even average players), it takes around 45 minutes and bad parties will wipe, hopefully making you a better player by realizing what you're doing wrong. Doing this fate 'exploit/whateveryouwannacallit' gets you 130k exp in 10-15 minutes by pressing one button over and over in the same spot.
I'm not really opposed to people doing it for exp. I mean, whatever. If SE wants to nerf it I encourage it. If not, I encourage that too. While I agree "bad players are just bad players" to be true, some players could really benefit to having to do a moderately difficult dungeon to level. Let's face it: pick up groups are always going to be hit or miss. But if people rush to 50, I'm under the opinion that it'll be more "miss" than "hit." I even previously reported this, but mainly due to leveling with 50's who didn't know how to target or mark enemies without explicit instructions. :|
TLDR: I don't care how people wanna play the game, I just hate how it effects later game PUGs. If it's your 2nd, 3rd+ class, have fun. You're likely a good player already. I just want better players in the community.