It was said with the new classes PWI would make leveling easier. Now that most of the people that would charge to get RB2 level 100 asap have done so, I'll just say that there's currently enough ''pink quests'' to level a char straight to RB2 lvl 100 without having to do anything else. Your movement speed is doubled if you're below level 100, even when rebirth. And the sky level quest chains are available (you dont need to have a certain sky level to do it anymore). It's possible that the sky level quest chains are only available if you are actually in the right sky level tier, tho the quest chain I~X is all available and it appears to be enough to level you straight to the next tier, at least at the start.
For the people that dont want to start a new char because of how difficult it is to catch back up, it might actually be pretty easy to catch back up now