In this thread, you said that if you defeat the last boss you get a cape which I guess was terribly misleading. Patch 6.85: Expert Mode Raids
“Expert Mode Raids feature twists to the existing mechanics of the raid in additional to tougher scaling in general and are meant to be incredibly challenging. They reward Level 21.4 gear, as well as a new cape if you can make it through the entire raid and defeat the last boss.”
Yes please. Not sure why this isn’t the case now. The cape is an achievement for a kill. Seems kind of silly to have to kill the boss numerous times to roll RnG on an achievement cape.