I'm gonna ressurect the thread so maybe PA notice this issue finally.
The problem is not that mechanics are hard. IDK if anything changed, but there is no RNG involved.
The problem is that some classes (like Succession Maegu) literally cannot complete it - our only float/knockback is "Tag" (RMB) which has 6s. cooldown, while the boss requires you to hit it like every 3s.
I know there is a way of doing it, consisting of running to the other side so the cooldown goes down, but it's even more tidious and unfun.
The other issue is the mechanic requiring a back-attack - also not possible on some classes, like Guardian, with not enught movement skills to land it in such a short time frame.