Mechanic spoiler for Yian:
I still don't get the mechanics for Agrias. I assume that when she is doing the long-cast raid-wide, I had to go to the shield duty action area, and use that duty action, and stay completely still so I don't lose the buff. I got the buff, and it stayed on my buff bar, but then I got knocked back and vuln up anyway. Does anyone know the "proper" way to do it?

You also have to face the target. You kneel and prop up a shield, a lot like Passage of Arms, but your shield has to face whichever monster is using an attack so you're able to block. And like you said, you have to be perfectly still, like Passage of Arms again, any action or movement will cancel your crouch.