Level Syncing isn't the best solution

[Astrus]

GW2 is another, and it's quite nice.

[...]

GW2 works insofar as it doesn't let you just clear the whole map. A synced down level 80 is still outperforming a player at level 20 even when both get synced down to level 18 for the area they are in. The additional skills, traits and equipment upgrades make a world of difference.