I am against this idea, I like the way level syncing is. There are certain abilities we don't have access to at lower levels that would break dungeons or make them too easy. In particular any mitigation, stuns, CC, DoTs, etc. Having a full level 80 rotation available to you in a level 30 instance, no matter the downscaling, still means more dps.

The way the level sync is at the moment means that new players have fun with new content and veterans get to help them push forward with their queue times. Level sync is entirely about the new player's experience, not yours.