Yeah, they should be brought back in my opinion, but with higher respawn and pokemon percentages. It's not fun having to run 255+ steps just to have a 5% chance of them even having an item, let alone a pokemon. But I digress, I would love to see them come back with new pokemon and hidden abilities.
New pokes would be nice, what about legendary's from previous gens with a 1% chance like dragonite was? Also better items lucky egg, master ball, and other held items