EX primals are traditionally intended to be the hardest content for casual players while also allowing a transition for raiding players into savage content. As far as that goes, Byakko Ex more or less does the trick with the consideration that hardcore players have already gone up to o8s in the first day.

I've definitely seen people make mistakes on that fight. What's funnier is that the worst players I run into in there seem to be players rocking full crafted sets that somehow even underperform compared to people below the ilvl requirement for it.