Genbu ignores Tempered Will

Date & Time: March 21, 2018. 11:23 PM (AST)
Frequency: Always
World name: Faerie
Character name: Magnus Brighton
Retainer name: N/A
NPC name: N/A
Monster name: Genbu
Class/Level: Lv.70 Paladin
Party or solo: Party
In-game time: Around 1:00 a.m. ET
Area and coordinates: Hell's Lid (x12.4, y1.7)
Housing: N/A
Steps:
1. Use Tempered Will before Genbu casts Hell of Waves

I've only tested with Tempered Will, but it's possible this happens with Holmgang, Surecast and Arm's Length as well.
I'm not sure if this is the intended behaviour of this attack, usually attacks that knock me back can be negated with Tempered Will. If this isn't a bug, please disregard.

Some knockbacks can't be negated.

If it didn't work, that means it can't be. As simple as that.
Besides, it wouldn't bring anything to nullify that knockback since we have the time to position ourselves before the barrier appears.

Yeah Surecast and Arm's Length doesn't work for that attack either, but it's nothing worry about. There is no environmental factors causing instant death so it's all good.