as seen above, your helmet has to much ias (if loh+highlord or cat)
let`s see
demon decrepefied is not such an easy thing to say since they all have physical resistances, don`t they
I doubt that you achive more damage with brand than with a wf yourself but let us leave that out right now and concentrate on the other things

let us assume we fight diablo on players 8, as you said you do that with this build

maximum ma speed= 3,5 attacks per second
diablo on players one has 113812
players 8= 350% more life=512154 hp
45% physres
one hit with cb would remoce14226 hp until his life would be the same as players 1
your merc can do 4 jabs per second (treachery+obedience+andyx or tal ias) his jab is 2 attacks--> 8 attacks per second at 40% cb
Quote
Damage to demons 2084 - 10268
Everything Else 1370 - 6493
diablo has 45% physres and is a demon
so you have 6176 avdam/arrow
84% ds=1037568
16% w/o ds=98816
--->11363 avdam/strike
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diablo receives 11931 damage/arrow when dec works

11931*3,5=41758 dam/ second
if our merc only triggers 3 times cb in that second, he deals more damage than you do
not even considered off weapon ed and his own weapon damage