You can get some cool upgrades for pretty cheap. You've got to get Lacuni Prowlers on your wrists, because they'll give you another +12% movement speed and some IAS as well. You should be able to see quite a bit more DPS from this upgrade for only 2-6m. Your belt could also get a serious boost from Inna's Favor for only about the same price. Other upgrades will probably start to get pretty expensive, but I'd like to see you get a big DPS boost from those items, and the Lacunis bringing you up to 24% MS will be a huge improvement.
To answer your question, yes you would get both CC bonuses from legacy/new Nat's if you had 2 of each. Many people go that route.
Also, I feel like your Vault rune should be Trail of Cinders, since your build is primarily geared to deal damage.
- If you're running through low MP levels, you'll want to focus active skills on dealing damage and get your movement speed from your gear and the Tactical Advantage passive. I recommend having at least 1 hatred spender that doesn't dump off your hatred quickly: Chakram (Shuriken Cloud), Sentry, Rain of Vengeance.
- If you're running mid-higher MP levels, you'll need to focus on survivability and have a strong combo of 2 hatred spenders that deal damage at a distance. A build that has worked well for me at MP 5-8 is: http://us.battle.net/d3/en/calculator/demon-hunter#aQYgVk!efU!YcbYbc