The only way to not punish those that want to grind endlessly on one job but reward the people that only log in a few times a week for a few hours, is to use WoW's model of rested xp. This has been said since fatigue first came into the light during closed beta 2, and went completely ignored by SE.
The current system in no way helps anyone, because as Kuro said, anyone that's motivated enough will still be able to push through surplus and level, and it's not going to matter in the long run anyway. There's nothing to do now, regardless if you barely play and take your time to 50, or you're already at cap, there's nothing when you get there except a few world nms and crafting. Yes, content is being worked on, that's not the point. The people playing now will either be 50 by the time the rest of the world (PS3 users) starts playing or they're going to quit the game long before then so the new people will be at an automatic disadvantage anyway from the start.
The system as it now needs to be replaced, it hasn't worked, and the only reason it's in place now anyway is to stop people from reaching level cap before content is added.