Barrier mechanics

Does Barrier prevent AoE/status Damage? I’ve noticed I’m able to kill a Blood Reaper that already proc’d his ability by attacking a different enemy with Relentless Hunger or Razorsharp.

No it does not. Barrier, Shell, and other such defenses only affect the attack itself.

If the barrier isn’t broken, it acts a lot like shell, and will cancel status changes. However, it won’t stop extra damage attacks like shell will (which cancels the attack altogether). If you break through the barrier, even doing just 1 damage, all effects will take place.