Statistics ? Statistics prove nothing since there is no statistical value that can describe ballance of a champion
you can compare winrates damage survivability downtimes etc etc ... and you still get left with no indicator of actual power
the only true indicative is how strong does it feel for player who plays it and player who plays againtst it ... and even those are vague
many people find themselves unable to defeat a riven
and many people find it hard to win as riven
but we never hear of rivens who do just medicore ... not too opressive and not underwhelming
thats the same case as yasuo in my opinion ... thats why i consider it a problem
champion cant just be pushed out of some games and dominate others because of some factors and be left with no middle ground