The state of level sync in dungeons:

Right now the amount of health and damage mobs do in level sync dungeons are based on the circumstances that the players have gear within 5 levels of the level sync cap and players know how to play their class. The bestiary hp and damage relationship with the level sync is especially apparent in dungeons like Dark Hold and Aurum Vale. Aurum Vale is just plain unforgiving for a level capped dungeon and often takes 35-45 minutes to complete being forced into level sync. While uncapped dungeons can be steamrolled in 20-25 minutes.

I can see why the China servers removed it, they pay by the hour. They need to make the most of their time.