As someone who recently made a new character and is doing Gladiator as its main, let me tell you: Higher level characters, even synced down, can rip hate off HARD from my character, just with their current synced skills. More so if its a White Mage spamming Medica for some reason. If I had more green equipment rather then white equipment it would probably be easier but that depends on drops, which haven't been in my favor.

The leveling roulette to give you a reward for helping newbies (usually, as sometmies you don't get newbies.) And it isn't fun for newbies if you and all your skills from later on just break the dungeons. Scholar fairies already show how broken lower level dungeons can become if we let ourselves use all our skills from later on.