I think your ideas aren't too bad. The open world dungeon would be pretty cool though I think they need to refine their creation method. At the moment, after the Diadem, I wan't to see them experiment with revamps to that till they start to figure out what works.

I see Hunts as a much harder problem to solve. Hunts naturally are susceptible to zergs. Unless they actually restrict the number of people who can access the hunt, which would be very unpopular, any open world hunt using the current model is susceptible to zerging.

That said, I think the FATE chain system could be expanded to be much more engaging and rewarding as open world content. For an example I would point to the Darkscale FATE chain. In that chain, by completing successfully the FATEs linked to Darkscale's lieutenants the Darkscale FATEs themselves are slightly different and as a result there is a bonus follow up FATE which rewards a huge amount of EXP (the most I've ever gotten from a FATE) and a barding specific to the special FATE. Having FATEs that lead into each other could make the FATE system much more dynamic and have an escalating chain that if successful triggers special FATEs that have special rewards.