I don't even know where to start with how wrong this post is /facepalm
For starters, you're thinking of 8man when you say people have killed NiM Kephess.
You don't need everyone in BiS for NiM Kephess 8man and it's a joke compared to 16man. End of story.
I specified 16man- last I checked
only six guilds have even gotten to Kephess on 16man, and
nobody has killed him yet.
Considering how incredibly tightly tuned that fight is, I'd say yeah anyone working on that fight who is 66 cunning less than what they should have is in fact doing it wrong.