besides the fact blizzard balance philosophy ensuring dumpstering sooner or later, there’s the part where too much pressure will be applied to the tank player to play the “correct” meta tank and also perform ultra well since in the case of raid bosses the matches will revolve squarely around them.
basically it will boil down to eho has the best raid boss and who can kill the other first.
Imagine having your entire match decided by the tank player picking sigma over rein in a hypotetical rein meta