I just got him down and wanted to throw a post up ! Wanted to get him before 1.0.3 speed nerf and until inferno difficulty changed so, yay! I found the thing that did it for me was first rotating blind and serenity when fighting shadow clone ( to watch out for the stupid bell) and then just watching diablo to make sure you never miss interrupting his fire ball ( cause that hurts !). Dont look at your HP or your buffs , you know when you low or your mantra is down. Just watch him and never miss a beat.
I also figured out that resolve > seize the initiative. ( 25 % greated then my 1400 dex to armor which is 10 %)
stats 21k dps with blazing wrath up
780 resist all
3.8k armor ( I was at 5.2k with seize the initiative but resolve is better cause 1300 armor is only 10% reduction)
800 life on hit
2.38 attacks per second
I used a 900dps dagger with 1.89 aps and 300 life on hit socket ( 1.25 mill on AH , a steal ) and a shield
The most i spent on my gear pieces was 1.25mill for dagger and rest was 800k or less.
I skipped some champions packs to get to him cause i was excited, I just ran thru the spire level 2 after izzy haha but i could handle about 60% of the special packs, For special packs i used this build.