I don't have a problem with most of the content being instanced. If that's what the majority of people want, then maybe that should be the majority of content. However, 20% is also a number worth paying attention to. There is /no reason/ why we can't have mostly instanced content while still creating the interesting and dynamic open world that 20% or more of players want. Players can participate in what they want. Rewards can be roughly equal between players wanting to participate in only instanced content versus those who want to participate in both. Powerful items from an HNM scene can have their rough equivalent dropped in instanced raids.

But there's little denying that the current open world is pretty bland. I'm looking forward to the zone redesigns, but NMs that are not always sitting up (and NMs that drop crafting materials as well as the exclusive items) would help greatly to spice it up. Instance raids are good and fun, but when you only have things happening in instances the rest of the world becomes stagnant and dull. Having NMs that rotate spawn times or placeholders help make sure there's always something going on. It creates a more realistic, dynamic world which has a direct effect on the entire psychology of the game.