I'm new to this game, and I may be lucky to get to 50 before HW arrives (currently 22, just started Sunday). Ok, so I'm months, nay, years behind, but know what? I really don't give a fuck. Game does level syncing properly for high level players doing low level content (namely fates and dungeons). My friend's able to come along and run dungeons with me. I have other friends on the way and I'll be able to do the same with them.
Back in my WoW days, I pretty much ran every single dungeon on any alts while I leveled. This game basically has you do the same thing via the story questline (or at least it has up to the point I've made it to). Could be frustrating if you aren't a tank or have a friend who can tank, though.
As others have noted, the whole game is a new experience for new players. I'm enjoying it thus far, despite the whole "months behind" thing. I don't care. The whole end game raiding thing hasn't even crossed my mind yet (and won't until I'm 50).