There was an article posted during the media tour that quoted that leveling alt jobs would be a lot faster as they'd prefer people to be able to enjoy the character over just the job. In Jessie Cox's interview they mentioned something about increasing side quest exp. My guess is they didn't change the exp curve but rather the sources that give exp.

For anyone the thinking it's too fast already, just remember that many of us here on the forums have leveled every job over years. The response is likely due to the influx of new players, it's a bit daunting to try out new jobs and roles when there's 19 to level and 20 to pick from lol