I dont know why they dont do it like WoW. You keep all your skills even when playing a dungeon 20 levels below but everything automatically gets synced to that level.

MY biggest issue when leveling a new job only with roulettes for instance is that i usually get low level Stuff until i'm almost max level with that job. Then suddenly i get a near max level Dungeon and now have 20 skill i don't know what to do with cause i was never able to use them. I literally can't learn to play the job when placed in low level dungeons.