You understate your point: the 83% rate is much, much more than 3x worse. To kill 100 intended targets, a 28.6% civilian death rate means you'll need to kill `N / (100 + N) = 0.286` (N = 40.06) civilians. With an 83% civilian death rate, to kill 100 intended targets, you need to kill `N / (100 + N) = 0.83` (N = 488) civilians. It is about 12x worse to have an 83% civilian death rate compared to a 28.6% rate.
