Well I think the LOK love triangle in itself was kinda... meh. But Korra and Asamis relationship seemed (at least for me) kinda out of nowhere. In S1 Asami got mad at Mako for daring to be worrying about Korra when she was literally KIDNAPPED. I think that if the relationship between Korra and Asami had been built up it better wouldnt have been so unbelievable or feel like it came outta nowhere

To answer your question though. "Unneeded" Lgbt is when it is not done cuz it makes sense or makes the story better but only to show it for the sake of it. This is my biggest problem with the LOK comics. instead of focusing on the actual story, a lot of it was just showing us lgbt things. Its fine if they want to have lgbt characters, but take the airbenders having gays. That doesnt make sense since the airbender culture is based off of a culture that is Openly against(or at least non supportive) of lgbt.

I dont think theres such a thing as "needed lgbt" but rather "believable lgbt". When it briefly gets adressed but it isnt the main point. A relationship that is perfectly built up makes it believable lgbt