Is there any guide on the farmable sets like Armor of Arkkhan?
As far as I know, new sets in Grimarillion drop randomly.
Easy way: activate maximum Hero spawns via Plutonium Nyborg on the Ultimate Difficulty and go farm loot from Aetherial Heroes in Burrwitch Village (you will also get a lot of Forgotten Souls which can be converted into random Diablo epic and legendary items).
Hard way: farm loot in the Shattered Realm