That strength in numbers thing is a nice idea, I've never heard something like that before. I dont think dungeons without trash would be good... I mean, that's what most raids are, where would be the difference then except in the number of people? I wonder if harder dungeons would work if they put a written explanation of the dungeons mechanics in the DF description, would people read it then and understand mechanics better (the ones who want to do it blind don't have to read it)?
I would like jumping puzzles, one person has to make it to the other side and activate a bridge for those who didn't make it, I would love to see that sh*itstorm of rage. Although I really actually like jumping stuff like GW2.