It is more about learning your class, eg. Hellfire is learned on 22 and is usable in both froms normal and uber-super-cool, in both forms gives you fury. And for instances farming 22->62 (62 you gain immolation aroura) gives you an option to be doing solid AoE in meta while generating energy for boss bursts of Touch of Chaos.
No Demo is not nerfed leveling spec, only thing that is a pain is extreme long shadow bolt cast time. But during leveling Voidwalker will do everything for you Tank and Spank. All you need to do is throw corruption on as many targets you can survive and thats it .
Again. It is about learning your class, skills how they work. And even if for me HoG felt strange it was nothing really bad
. It could be made usable in Meta form during early levels like up to 70 or something. But again, how fast you do 1-60 probably in less than 8 hours played. Yesterday i went on and made a test how fast i can do first 40 levels, it took me 3 hours of played time without any stress. Longest run was the run for mount at 20.