I'd honestly like to see harder enemies using more power sets or something custom players don't get. Right now at 50 + incarnate stuff, there's really not much of a threat or sense of challenge/danger outside of some of the Incarnate trials. Status effects are a non-issue when you have enough set bonuses you can just tank them, and holds vs any sort of melee char...the enemies may as well not bother.
I'm not too sure what can be done, since nerfing isn't the...right call in this situation, especially since it would have people calling for the guillotine.
Like I mentioned elsewhere, I feel challenge and content (as in stuff to do/story/new enemies) is my own personal top thing. with powers and such being a bit further down.
Like mission variety, I'd like to see defend objective stuff, like as an example, the cape mission where you have to protect and item from the rikti destroying it. Or civillian rescue missions where they can die from enemy attacks rather than just sitting there cowering.
Heck more enemies like Longbow Nullifers would be nice to, make some of us pimped out IO users sweat a bit