Set bonuses apply when you have enough slot for that set. For eg, to use nadroji bonus, you need to sacrifice 2 set affix slot for the bonus to activate . Also no two nadroji bonuses can't activate at once so you can't have 200% enemy rarity like that from my experience.
For druidic bonus, you need to sacrifice 4 set affix slot by making druidic be there. For epiphany bonus though, you don't actually need a set for it to activate though you need a set to be able to reach the requirement.
For epiphany bonus, all you need is 70% attack speed on gear and epiphany set affix for that to happen.
As you can see, most bonuses aren't worth it because they sacrifice potential set affix slots just to activate. All sets cannot force the bonus to activate as well but the only way you activate a bonus is fulfill a requirement such as use 4 druidic (meaning have 1 head , 1 chest, 1ring, 1 amulet have druidic set affix) to activate the bonus.
Epiphany bonus is probably the only truly viable bonus because it doesn't require you to sacrifice many set affix slots but to use epiphany and get 70% attack speed on gear.