Level sync doesnt have to be like how it was in FFXI.

If they did it right they would work like this:

Level 46 player wants to play with her level three 30 friends, so she joins their group, level syncs, and now she has the same amount of power as she did at lvl30. Now they can all group together and do toto-rak and all get exp and it will still be challenging, but the level 46 player's exp is somewhat reduced so her progression to 50 stays at the same rate.

They can give the higher level player gil/seals/special item rewards for level syncing to help lower level players fill their groups, and this will act as incentive despite the reduced EXP.

Level sync should only allow players of disparate levels to play together and be rewarded. It shouldn't allow anyone to level up faster.