Okay awesome, so it seems like 9k is the good range to be for reflect mitigation.
Any other testers out there are appreciated as well.
I went back to try yesterday evening after your enlightenment:
1. Increase my armour and AR with IK chest/belt & WC & Iron to be 800AR & 10500 Armor
2. I can manage to fight off MP10 RD in a pack with SMASH and REND
3. But when it come down to single mob, i feel the RD is coming in again not much but definitely can feel the HP is going down
So i guess RD still coming in just that my REND save me in action and REND is not coming in when im only facing 1 mob. Still doable with 3% LS with 1k armor and 800AR but with just 6% LS i can do much comfortable with 660AR & 7k armor.
This is my side of conclusion.
It should come down to a matter of your LS and DR outpacing the RD damage. What I have below is based on a reflect damage percentage of 15, since that is all I could find for 1.06 (stuff I have seen says this will be nerfed in 1.07).
So in your first scenario you had 10,500 Armor and 800 AR for reductions of 76.92% and 71.74% respectfully, which equals a total DR of 93.48% for 63mlvl mobs. So for a 100k hit, 15k would initially be reflected at you, which drops to just over 977. If you have 3% LS your LS is actually 0.6% in Inferno, so you are stealing 600, leaving you with a 377 gap, or 40%. Keep in mind that LoH is applied during the hit, so before any RD damage. A LS of 5% in this scenario, get you to even.
In the second scenario you have 7,000 armor and 660 AR for reductions of 68.97% and 67.69% respectively, which equals a total DR of 89.97% for 63 mlvl mobs. Again, a 100k hit, your reductions drops the damage reflected to 1,503. 6% LS gives you 1,200 returned for a gap of 303, or 20%. A LS of 7.5% gets you to even.
So if you are hitting really hard you can see that the scenario where less armor, AR but more LS closes the gap more effectively than more armor and less LS. However, in both these scenarios you are still losing. Also, any elite damage reduction should apply as well and close the gap above. So if you elite reduction is even in the two scenarios, the second scenario is still better because the gap will be closer to being covered.