I like the idea of the DF dungeon list resetting for each class so that you have to clear each dungeon once before you can run the next, so that you have to have run all dungeons at least once on a class before you can even attempt the hard mode primals. If you wanna level your class up to 50 using just fates, you still could, but you couldn't just ride the fate train straight to end-game party content. It would still help, though since you could run each dungeon knowing you're the maximum possible level, and hopefully you've done something to have at least level 45-50 gear so then you could just focus on learning to play your role through most of the DF content.