Riot changed the ARAM random champion selection algorithm

Since the launch of preseason patch, I have played several hundreds games in ARAM mode, and I definitely sensed that Riot has adjust the random champion selection algorithm so that you get short-ranged champions more frequently than before. Of course the algorithm has been never absolutely random, but it is so clear to me that they have adjusted the probability to get each champion. That basically made those ARAM accounts with only ARAM op champions even stronger, and made the normal account players with many short-ranged champions suffer in ARAM. I wonder what's the point of doing that.