I was inspired by this question that helped me get to Diablo.
How to defeat Rakanoth as a Demon Hunter?
But now I am having trouble beating Diablo himself. I can beat the first one, with the help of health pools. I then can kick the snot out of myself in like 2-3 hits. But I can not beat Shadow Diablo.
Can't use the Templar which had been a big help.
I just did something I said I wouldn't do. I broke down and brought a chest armor with +20 to all resistance and still I can not win.
Edit to the correct amount
I currently do about 1893.35 DPS and have about a 12,122 hp, with +10 life per sec. 1483 armor
I am on Nightmare difficulty. I just reached level 51.
Any suggestions on a build and skills? Should I do more act3/4 clears to get to a certain level for a certain skill?
UPDATE I am moving on to Hell
Thank you all for your help. I gave most of you a vote up, but I am only allowed to give one correct answer.
I tried Ben's Answer first, and I died 4 times before moving on. While it further progressed me, shadow me was too strong and killed me either the first or second time.
I tried yx's suggestion twice next. I never got away from Diablo and he was very hard to kite.
I tried Stephen's suggestion next. The first time I messed up which button was which and Vaulted right into a cage (actually I was just outside but it still stunned me). The second time, I whooped butt finally. The Vaulting helped. The Preparation with Battle Scars was useful in the shadow world, it was like an additional health position.
I am sure ayckoster's suggestion would have also worked. In fact if you take Stephen's answer and replace Entangle with Hunger Arrow, that may help with Hatred regeneration and still hit from off the screen.
I leave this up here for any passersby.
Again thank you all