EDIT: thanks for taking the time to test that DOM
Always, forever, in every computer and no matter what 2 x 4890 I'm using when I run CFX both cards only run ~ 40% tops except an occasional spike. Usually each card is at a fairly steady 30%....which never made any sense to me. Each card alone runs ~90% or whatever it needs. I verified that the core clocks are coming up from 240 to 1000 when 3d starts.
Dropping to like 4x or something you mean? Pretty sure it's not and it is a newer board(CHIV).