1) PLing is not about increasing your chances of success. It is about eliminating your chance of failure. Some people need to feel like they are always succeeding so they do everything they can not to fail. In most cases they are not looking for the usage of the class so much as a few abilities not inherent to the class they are playing full time. A built in flaw of the armoury system. Kind of like leveling every sub job in FFXI that you can to exploit the best one in any given situation. Just apply this same logic to leveling almost everything in this game.
2) Pling/fast exp rates as a whole cheapen the experience of the game. It is not about grinding or not grinding. You are missing out on meeting other people in game and learning the class you are playing. You also miss out on tactics you may or may not have seen before. Sure we all want to level quickly but half the fight in other MMO's is how to play as a team to better our gains. If the party aspect of this game is going to net more exp then teamwork should be the focal point of that. Exp chains were supposed to personify that but without BRs and the new way of combos they are putting it back on the individual to perform on their own rather than the group to perform as a whole. There are individual skill sets you learn for soloing and group skill sets you learn to compensate for one another in a party environment. The latter is sorely lacking in this game because most feel the need to be a "superstar".
3) People are complaining about level 50 content. What about the other levels? Did you notice them as they zoomed by? More than likely you did not. I think when they eliminate guild related skills for guildmarks they should still leave the quests and add three more for each class. 1 for every 5 levels after 20...as limit breaks. Make them with a stretch though (ie. level 40 limit break can be done from levels 38-42 but must be done before you can reach 43). As it stands I can level any class to level 50 without ever going near the guild. That needs to change.