Source : http://na.op.gg/champion/ahri/statistics/mid
The disparity between Glacial vs Classic Ahri get even bigger the higher elo.
The slow from glacial is so good it get rid off her main counterplay (dodge charm) with barely any trade off because the extra damage from GLP compared to Luden make up for electrocute in all in, and cheap shot make up for electrocute in lane.
The nerf is her ult cooldown but glacial Ahri doesn't even need ult to make plays she just need GLP or twin shadow active. While classic Ahri with Domination/Sorcery highly rely on ult.
The trend of Glacial Ahri started when her charm duration, twin shadow and glp got buffed.
As a classic build Ahri player I feel upset about this.
I'm not saying Ahri shouldn't be nerfed, but Riot does it wrong.