The nerf's not even that bad with the Dex to Armor Conversion:
Using this for Calculations:
http://d3resource.com/mitigation/Assuming 10,000 Dex, 5k Armor from Gear, and 25% from Paragon = 18,750 armor
30% damage reduction for being melee class
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5 All Res, 1 of Each Res
500 + 250 + 8 = 758 allres
160 *.3 * 5 = 240
Fire = 758 + 160 + 240 = 1158
Cold = 758 + 160 + 240 = 1158
Lightning = 758 + 160 + 240 = 1158
Physical = 758 + 160 + 240 = 1158
Arcane = 758 + 160 + 240 = 1158
Poison = 758 + 160 + 240 = 1158
Total Mitigation after Armor & 30% Reduction for being melee: 97.444%
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5 pairs & 1 res
250 + 8 = 258 all res
320 each res, poison res 160
320 * .3 = 96 | 160 x .3 = 48
Fire = 258 + 320 + 96*5 + 48 = 1106
Cold = 258 + 320 + 96*5 + 48 = 1106
Lightning = 258 + 320 + 96*5 + 48 = 1106
Physical = 258 + 320 + 96*5 + 48 = 1106
Arcane = 258 + 320 + 96*5 + 48 = 1106
Poison = 258 + 160 + 96*5 = 898
Total Mitigation after Armor & 30% Reduction for being melee: 97.353%, 96.912% for Poison
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Stacking 1 Res
250 + 8 = 258 all res
160 * 11 = 1760 targeted res (choosing Fire for example)
1760 * .3 = 528 res
Fire = 258 + 1760 = 2018
Cold = 258 + 528 = 786
Lightning = 258 + 528 = 786
Physical = 258 + 528 = 786
Arcane = 258 + 528 = 786
Poison = 258 + 528 = 786
Total Mitigation after Armor & 30% Reduction for being melee: 98.372% for Fire, 96.607% everything else