TBN is the most powerful shield of the game, Xeno don't like it bcs mix mitigation and DPS performance but the shield is just to strong and it's the primary reason why DRK have the best defensive kit against tank busters since any combination of TBN with rampant, dark mind or shadow wall making you laught against them.

TBN is at the same time the only unique mechanic the job remain after the identity slaughter SE comit against the job, the shield meaby need a nerf of 5% to make it more easy to break and DRK don't reallly need all that mitigation but outside of that the skill don't need changes.