You don’t need a huge shield like Wizards do, a 300k-ish one will do just fine, what you need as DH is AR. To get most toughness you need 10:1 ratio for armor vs AR (unless this changed in past 2 seasons and I am not aware of it).
You will grow armor naturally by gaining paragons as your main stat is dex which also increases armor for every point you spend, so you need to focus on AR.
For me on HC - I crafted ancient Crimson3pc belt and pants with an int class, aiming for as close to 650 int rolls, high vit, 120+ AR (%15 life on belt ofc), and am also using a Squirts with int roll main stat, chc/chd/socket. This puts me at 2k int base (that’s 200 AR), plus AR on most pieces of gear 120-130, with boar companion (20% more AR) I manage to get close to 2k each resist type with ~24k armor.
Obviously you will aug with Dex unless you’re 6k+ Paragon, then you could go for couple int Augs to catch up on AR to your armor.
Life regen is nice on defensive items (at expense of armor, but not %life if you can get it - at least for me on HC due to bugged Raziel), on offensive items always go for what you need most (you should be at 100% uptime on Vengeance, and more CDR doesn’t do much for your dmg, so go for RCR once you hit the highest MS breakpoint you can w/o gimping your chc/chd).
RCR does two important things for you:
- provides toughness through CC3
- reduces your hatred and discipline costs - my HC DH is close to 70% RCR, my MS costs a mere 7 hatred, so even with speed pylon and 21 frames BP, I am not dipping under 90% hatred pool using 1 Evasive Fire Hardened every 5s to keep up Wraps of Clarity buff (also your smoke screen if you are using it, or vault will cost almost nothing).
TinneOnnMuin touched on this as well, regarding RCR vs life regen, a leveled gizzard to 100+ is plenty for your shield.
But once more, do not ignore AR. Damage is reduced by armor / resists then what goes through by your DR, so if you have poor AR and the number going through is as high as your HP+shield after DR you will get proc’d, simple as that.
PS: you can get at ~2k para with good affixes, ~96% DR with squirts on (goes to 97.xx% when squirts buff drops, but you shouldn’t have it drop ever).
Cheers! <3