This game needs an experience gain toggling option. That way we won't massively out-level the non-instanced open world questing content while going through the main story content.
For example, I want to be able to lock my experience once I hit 50/51, so when I unlock the first expansion I'm not way over-leveled compared to people who experienced it when it was first released. The same applies for every following expansion. It's impossible to prevent your character from becoming over-leveled before reaching the open world content intended for that level. Currently, the only people who get the privilege of experiencing the content at the level it was intended to be played at are those who were at the level cap when expansions go live. I was lucky enough to be one of those players. However, I still would like to play through the story on alt characters sometimes.
This problem can easily be fixed by putting an option in the character configuration to toggle experience gain.
Not everyone who plays this game wants to madly rush through the content as fast as humanly possible to get to end game raiding. I'm sure many people would like to experience content at the proper level, as it was experienced by players who were active when each expansion went live.
I'm well aware of level syncing for instanced fights, and I truly appreciate that feature. But that instance level syncing does nothing for open world quests that are not instanced. I know I'm not the only player who would appreciate this feature.
If it is an optional setting, then there is no downside to it. Those who want to level up as fast as humanly possible would still be free to do so. And those who want to experience the open world quests at the proper level will also be free to do so. It's s win-win for everyone. And something like this should be pretty easy to implement.