I waffle back and forth on this issue.

On one hand, yeah, it would be nice to always have all of our abilities available.
On the other hand, if they didn't nerf anything, a synced max-level character would absolutely destroy stuff in low-level content.

So why not nerf the damage a bit (or other more-complex solutions) when you're synced? That's a surprisingly tough balancing act. Nerf the damage too much, and people will complain that a level 17ARC does more damage than their max-level BRD. Don't nerf the damage enough, and people may complain that max-level characters are too OP when synced. Nerf the damage juuuuust right, and people will still complain that they have to actually do their full proper rotation, just to keep their damage on par with a lowbie with 5 buttons to push.

I would definitely like to see them figure out some sort of solution that lets us use all our skills while synced, but I do not envy their options. People will complain, no matter what. To be completely honest, I don't expect them to ever implement this.