Fending vs. Slaying accessories at this point in the game

[Seshayn]

Yes.

Certainty is important for high end content. Certainty is the difference between life and death 10 minutes into a hard raid boss.

You are so wrong. If you have any certainty in a real raid encounter 10 minutes in, you're either getting carried or not doing it before it was cool (aka overgearing it/post-nerf)