A personal anecdote before bedtime...
I too thought this was a terrible idea at first. It seemed to negate the effort I put into levelling up. I'm not the greatest player so I did side quests, FPs, WZs, etc, to gain XP and make things easier. So I was against level sync because I thought I was doomed to struggle more than I already do.
And then, I tried it.
I was 46, on Hoth for the Story quests. I ran a solo FP (Esselles) and jumped to 48 in there, with no boosts. By the time i finished the Hoth story, I had hit 50... but was still synched to 42. I said, what the hell, let's give a Heroic a shot, what's the worst that can happen... i die and run away?
I OWNED it.
So I did another... and another. No trouble, no deaths, even without a healer companion.
AND the gear I got was FAR superior to the lvl 48 fully modded custom gear that I was wearing, I even found some relics, which helped ease the loss of my hard-earned matrix cubes
So yeah, I'm sold on level sync. That being said, I don't think it eliminates griefing at all... I did have someone sneak in and snag an objective while i was battling the guards. I HATE that....
This has been just one old man/new MMO gamer's opinion....