I'm playing on the Normal difficulty. I was able to procure and craft the Hunter's armour. The dark armour sets you talk about, in which chapter do I get the schematics for it?
The Dark Armour sets are exclusive to the Dark difficulty mode, so maybe if you enjoy the game and give it another go do try that difficulty.
Another thing, on the first run experience the Roche story arc only then choose Iorveth's story. Else you will fall like a sucker for the latter for eternity just like me.