Aren't there like almost 50 available? How would your described scenario ever happen? If you can play ~50 heroes merely to the point where you better afk in fountain to prevent feeding, then your team fucking deserved those -25. Obviously, I can see why one would be upset that a game mode was removed (Nere could have played RD ranked before too) so the only reason for this action I see is to make top MMR games more interesting. Clearly, games on that level technically concern only very few of us but perhaps Valve is sick of seeing the top MMR being inflated further.
Then maybe they can make it so if your MMR is higher than, let's say 5k, they disable all pick. This way us noobs can be happy playing dota.