You have 2 problems, resists should be around 1k fire/physical maybe even a little higher to do it comfortably. If you're picture is unbuffed you're close. Second problem is life regen, should be around 700-800 minumum preferably a little higher.
I'm doing act3 with 9,7k armor 1k resists fire/physical at 1100, 50k hp, 700 life per second (good alternative if you cant find life on hit). Using a 2H and at 27k dps, act3 is doable with 18k dps but its so much nicer around 30k dps that way you can destroy champ packs with 1 WotB.
Spec looks good, I use 7 sec ignore pain instead of threatening shout. And instead of superstition I use a dps passive or inspiring presence. You might want to try out inspiring presence or get some life regen on chest/belt/boots/shoulders its pretty cheap on the AH, or get some life on hit instead but that's more expensive usually.
I'm sure you're setup works too Winkle but act3 is fine with 20k dps and WotB if you have a bit more defensive stats, the only reason you get away with your low resists is your high dps and maybe some more life regen to counter the damage?
Its either higher defenses or higher dps both work.