if you salvage Legend+ Items for Dust, you can use the Dust to get Legend & Eternal Items from the LegendEx. this is for when you need an Item NOW and can’t wait to get it farming.
NOTHING increases the damage of Crushing Blow except for Crushing Flames.
you should do a Search 
on CF/Frozen Builds to get an idea of what is possible, and see if any of your ideas can do as good as the others.
now, I have tried using Frozen, but my play style doesn’t work well with that Set, or maybe it is my mind set. maybe switch Frozen with some other Set that can give damage, like Pathfinder (if you have +50% Dodge or better), and Execute is a good idea with Demonic.
Electrocution means having Shock on one of your weapons or going Prismatic/Ascendant.
Mercenary only works with Swords, and I don’t know if Rogue Dagger is considered a Sword.