Main thing I like is variety. I don't want Argus to feel like the Barrens or like Northrend. I want different parts of the game world to be different. The other big wish I had for Argus - shared with Blizz in their forums - was that there would be a real sense of danger. That we would feel like we were operating in hostile territory. Invading an enemy planet should NOT be convenient. It should be challenging and we should feel like we're having to sneak around ducking for cover on occasion. That's how it would be in any decent book or movie about what we're doing. That's the experience I want in game as well.
My biggest feedback to Blizz atm would be that the new fel reaver adds (forget what they're called atm) need a less confined patrol; no one's going to worry about getting surprised when their path is so predictable. Should probably be some other dangerous mobs we have to watch out for, maybe flying elites that none of us could count on soloing. If we can walk into the Legion home world without our heads on swivels, we were wrong to ever worry about them to begin with. If they aren't dangerous, they're a joke.