How, exactly, do you think level sync works? It literally reduces your level to match the level range of the content you're doing. Your level does more than dictate how much HP and MP you have, it also determines what skills you can use. It's always worked like that. Lower level, fewer skills. Not even XI let you use higher level skills when synced to a lower level. I agree that the cross-class slot system works a little weird, but it's worked like that since 1.0. High priority skills go in the first slots, low in the last. "But they are all high priority!" The you need to pick the ones you really can't live without.