I think the writers struggled with finding a place for all these characters to fit around Nick. When Monroe came into the pic, Hank was relegated to just a colleague he did "cop" things with as opposed to the close relationship that was hinted at when they first eye Adalind across the street. Nick could only be himself (true and complete) with Monroe, who was a partner in every sense of the word. The longer the others (Juliette, Hank & Wu) were kept "outside" the worst the relationship got and suffered in front of viewers.
Rosalee is another that quickly found her place as the "healer" in Nick's arsenal.
The only other "honest" relationship Nick had was with Adalind, they were adversaries and played that accordingly. This evolves in the later seasons but I think they carried this "honesty" (albeit clumsily and hastily) into their romantic relationship. It wasn't lost on either that he was a grimm and she was a hexenbiest. They just found a way to make their weird unconventional coupling work.
Renard was a mass of confusion that only worked because of Sasha but his duplicity was eventually lost as he too assimilated to a honorable scooby until BC came knocking on his door.
Rosalee is another that quickly found her place as the "healer" in Nick's arsenal.
The only other "honest" relationship Nick had was with Adalind, they were adversaries and played that accordingly. This evolves in the later seasons but I think they carried this "honesty" (albeit clumsily and hastily) into their romantic relationship. It wasn't lost on either that he was a grimm and she was a hexenbiest. They just found a way to make their weird unconventional coupling work.
Renard was a mass of confusion that only worked because of Sasha but his duplicity was eventually lost as he too assimilated to a honorable scooby until BC came knocking on his door.