I sort-of agree. I don't think HNM's should drop all of the best gear. But free-roaming, open-world NM's should drop some great pieces.
I'm going to do what you all love, and reference FFXI:
Dynamis game you AF/Relics
HNM's gave you Defending Rings/Ridill's
Regular NM's gave you O.Kotes/Emp. Pin
Limbus gave you Homam/AF Upgrades.
Notice how half is Open-World, half is instanced. And that is just a morsel of the way drops went.
Again, I don't think HNM's should drop every great piece of gear. But should they drop some amazing pieces? Yes.
Instances should be giving out equally impressive drops at the same time (of course depending on difficulty/etc, we don't want hand outs).