Someone asked this same question during a concerted effort yesterday(someone complaining he couldnt level crafting because he couldnt play 8 hours a day started the conversation). One of the responses was from a guy who said it took 3-4 hours per class to do 20-80 using restoration, and that was with stopping for gear upgrades a few times(of course, once you have those upgrades you would just keep them for the other classes coming along behind). He also said that was with gathering his own mats, but i wonder if some exaggeration was at play.

Regardless, Jojoya is right that exp rewards have been greatly boosted. When i was leveling a HQ starred GC turn in was worth half a level(roughly), and ive seen people level more then once on the same class standing at the GC turn in counter since then. Unless someone found a hack to do multiple "daily" turn ins per class, that means they got more then 1 levels worth of exp.