I've been trying to level up some of my main champions and haven't had any luck yet. I've heard different theories on how S grades are calculated and I think it's an algorithm based on average player champion performance vs your past performance with that same champion. For instance I've heard if you get a high grade the game becomes more and more strict for you to receive that grade again.
If that is true though how is that fair to long term League players and 1 trick ponies? For instance if someone has like 1m exp on a champion and has gotten S's dozens of times before, it might be impossible for them to continue to better their self. They might not have gotten another S for weeks, while someone brand new on the same champion plays his first level 5 mastery game like shit compared to the other guy and receives an -S.
What about everyone that has already gotten an -S or higher already before the update? You can obviously track it since it shows on the champion info. Why didn't they get 1 free champion token for their work?