Cassiopeia has one of the lowest win rates of any mid laner and mage now
Out of all the champions that got changed for worlds she was the most balanced one to. I admit that Syndra, Orianna, and LeBlanc are all too strong but Cassiopeia only needed an early game mana cost increase to avoid the level 1-2 zoning, not a complete gutting of her early-mid base damages.
