So crit gearing should be ASAP, you get it on chest/helm/idols, this is how we keep dmg sustain high and clear faster. As you find pieces with flat crit, you should wear it if you have nothing else and just craft whatever defensive affixes you need (minion regen/minion hp). That set piece isn’t really worth too much, yes you get flat dmg, but only with the full set which takes up far too many gear slots.
Dread Shade (DS) is typically cast on Bone Prison (Bone Curse) to taunt enemies (if in arena) and in monos you’d just throw it down behind you or out of the way, then cast DS on it to empower your other minions. I try not to ever cast it on my mages/archers.