OG Nightsisters Are Kinda Trash | Has It Always Been This Way??

I have just recently gotten my OG Nightsisters up to snuff, so I'm able to play around with them, and I'm noticing something frustrating: they're kind of trash! I always thought they were a pain in the butt because of plague and survivability via revives and the zombie, but I don't know, using them myself, they seem incredibly terrible.

In this video, I show them STRUGGLING to handle G12 squads while they themselves are R7. It makes absolutely no sense to me. Have they been nerfed? Have they always been this bad and I just never realized? Do I have them modded poorly? Am I using the wrong leader? Does the positioning matter? There are many variable here, which makes this that much harder for me to figure out what the root cause is/solution should be.