Stats aren't the only thing that makes players more powerful the higher their level. We also gain abilities which would be completely overpowered at low levels because low level combat isn't designed around having those tools. Equilibrium and Fell Cleave would be absurd in Halatali. So would full AST cards, Collective Unconscious, Holy, Deathflare, full set of tank cooldowns and Assize. It would be very unpractical to try and balance synched players of all levels with players who are just leveled enough to enter the instance.