Last night we were trying Malkorok.
I had to turn off the UI's frames and swich to the default ones
cause ElvUI isnt showing the shield status.
After we tried spoils,
and yet again the frames didnt displayed the debuff you get at mathid room (cant remember the excact name)
Your frames are probably filtering out debuffs that you want to see.
/ec > UnitFrames > (frame/group name) > dropdown at right/middle > Debuffs > Filters