On the real money auction house, I’m not sure that all the good stuff will end up there. I mean, personally, I absolutely categorically refuse to buy or sell on it: Buying things for real money feels too much like paying someone else to play a game for me, and selling on it turns it from a game into a job. And I don’t imagine that I’m unique, here. So anything found by us folks will stay in the gold house. I suppose that someone could buy our items for gold and then turn around and sell them for dollars, but surely it’d be more efficient for them to just sell their gold directly?
One thing that I do expect to see move over largely to the real-money house is the reduced level requirement items, so get them while you can (I hope I can grab one, myself, today). My reasoning is that the best items the farmers find, they’re going to keep for themselves, to increase their farming efficiency. But the reduced level items can only be found by high-level chars, but aren’t actually of use to them directly, so they’ll have no objections to selling them.
On Demon Hunter building, mine’s only in A3 of Hell, so I don’t know how well my experience translates to Inferno. But half my skills are set up for slowing (Rapid Fire#Web Shot, Companion#Spider, and Caltrops), so even with duration reducers, everything is pretty much always slowed. The slowing amount doesn’t really seem to be enough against fast elites, in which case I try to arrange for my templar to tank them in the middle of a field of Caltrops.
Another way of slowing things considerably is to kill them. Most monsters stay very well crowd-controlled when dead. 
As an aside, achievements are fun, but they’re even more fun when you get them accidentally. I’ve been trying for weeks to get No Man Left Behind (keep all soldiers alive while raising the catapults), but always ended up losing someone somewhere. But the other day, I was going through a3 Hell solo with my DH, just trying to get through, and ended up getting it. And at about the same time, I realized that my wizard had gotten On The Wings of Angels (finish a4 in less than an hour) without even noticing it.