I'm already level 40 on my Ninja and only returned about a week ago. Its definitely faster now, dungeons reward almost a whole level when duty roulette queued, heck even Guildhests are now worth doing to get 1/5 of a level in 5min.
The Challenge log helps out alot aswell. Suppose that the +50% XP from having a level 50 job helps out ofc, but even without it i think its way faster than when the game first launched.
Hoping to reach 50 this week and starting to see the new content since 2.0. I'm both excited and dreading the pugs that will ensue for some gear / main scenario quests but i have time until the expansion so i know i'll get it done eventually.