pretty sure you are getting confused by semantics or the way they are labeling it.
for me
Missile Damage Reduction 6%
Melee Damage Reduction 31.01%
Elite Damage Reduction 13.51%
(yes these numbers are smaller than the sum of what I have on gear)
(however look at the ehp gains by stat
+1% Ranged Reduce 27,738.7
+1% Melee Reduce 37,799.96
+1% Elite Reduce 29,974.76
stacking more of one type makes every 1% OF THAT TYPE give more ehp. there are no diminishing returns in reality, only on the displayed %reduction. also I believe blizz has even confirmed there are no diminishing returns on anything except dodge.