Now with Golden Nug, Black Emporium and all other stuff that made the game easy you are able to complete it at any time, no matter your level. Just craft tier 3 schems with tier 3/4 materials and you're good to go.
Storywise it fits better after Wicked Eyes and Wicked Hearts and Here Lies the Abyss since those two seem to happen in a sense of urgency but between them and WPHW I could see the emergencies and curiosities of both DLC making the Inquisitor going for some exploration. If you more into challenge right after reaching Skyhold works pretty well too, since Inquisitor is settling and not yet ready to fight Corypheus.
In the end it doesn't matter much since there is little to no reflection in the main game so you should think "If my Inquisitor heard about this, when would (s)he like to investigate it?" It is better because it fits YOUR character and YOUR story and you have less chances to regret =D