Don't see what the big issue is with implementing a lvl sync for post 50 content. I wouldn't call it so much making veteran players weaker in the duties/trials, but making the content relevant for people coming up to the content.

It's already bad enough for duties like CM/Prae when you get two fresh 50 tanks who can't hold aggro against 4 ilvl130 dps, or even worse two fresh lvl 50 healers that not only don't know mechanics of fight, but aren't geared enough to heal for speed run pulls or Burn strategies. What are you going to do then? Kick them for being new? Hardly sounds fair.

Maybe to compensate they could slightly increase rewards for content the duties/trials are run for? (more light/higher zodiac drop rates). Also make it so any cutscene in a duty runs automatically?

Don't really hear any complaints about lvl sync for pre-50 content, how would this be any different?