So the primary scatter target takes the most obviously. After 2-3 scatters I often see my threat creep up. I hit lucid and switch to another target for scatter. If I start to pull again. I hit diversion. If something comes after me after that.. it's typically because the tank is trying too hard to dps instead of rotating threat.

There's nothing to be done at that point.

It gets even worse with Enchanted Moulinet since its so bursty.

TLDR: yes, those RDM are playing poorly