Why are Dagganoth Kings dead content?

I am an Ironman that needs to kill Dagganoth Supreme and I soloed for a bit but it's annoying and I want to spend all my slayer kills on supreme. I tried the grouping section for DKs and even hopped worlds at the GE trying to find people that want to kill the others. I could not even get a response. How is content that is required for BIS still totally dead for grouping?