100+ old quests to access expansion content...?

[Berethos]

Sounds like poor design honestly. But if somehow the writers did back themselves into a corner where this cannot be logically avoided, they could have at least made the quests as rewarding as normal quests. The fact that I am getting 4500xp from these when normal quests give you 13000+xp screams to me lazy design.

Or intended design, such that doing the quests won't put you too far beyond the intended level for the next steps when you reach Heavensward quests.

Kind of like how experiencing the story, and being required to, is intended design. Good luck convincing the developers to change their vision because you feel inconvenienced. You'll need a lot of luck with that.