I have been training constantly since September 2017 a legendary character in training grounds. That is 5 months straight constant training.
Not once have I seen a 5* from the grounds. Rarely I get 4* and constantly I get 3*.
Why are the results so pathetic? Placing dead last in all events I can earn a 5* character pretty much every month.
Training grounds need work. Maybe instead of characters they give tokens more frequently so that at least adds to the mix.
Either way it appears to be a total waste of resources but a decent way of hiding food and people.