From Reddit: NO level sync when entering a dungeon with less that required players!

[Felis]

They never said they were removing experience from the dungeons. =)

You would not get roulette reward, because premade parties can't start low level roullete (or how lv17-59 levelup dungeon roulette will be called again). What remains is the exp from the enemies. And look how much exp from a lv 17 enemy you get with lv 50 ^^

It will be more for farming gear for glamour or GC seals. Everyone who want exp will still do roulette.