I'm thinking Steffi Graf and I.Lendl. Graf's ball toss looked like it was more than 20ft. high, as did Lendl's, I'm not sure which is higher. In any case, it takes tremendous precision and timing to throw the ball in the same place that high and to hit it on the descent. I've tried it myself and wonder how on earth Graf/Lendl's serve toss wasn't a major liability. For myself, the toss is about 1-2ft higher than the height of the arm plus racket. Anything higher and the ball toss tends to wander around, and just feel "unstable". I agree that a high ball toss is more bad than good.