The QSS and Mercurial Scimitar active has two uses: cleansing crowd control (Amumu ult) and purging combat debuffs (Zed ult). These cases differ in that crowd control is setup, while combat debuffs are the payoffs to such setup. When you cleanse CC, the enemy needs to lock you down again to aggress on you, but that tends to bpretty reasonable ask. By contrast, cleansing a combat debuff wipes the applicator's primary means of fighting you. So, those champs are pressured to snowball before their effects become meaningless, while their opponents are forced into buying QSS even if it's incredibly inefficient to do so. This leads to destructive effects on game balance which we've left unanswered for too long. With the understanding that there may be outliers we need to address, we're unshackling combat debuff champs from their quicksilver collars.
ACTIVE EFFECT : The actives of Quicksilver Sash and Mercurial Scimitar now only remove crowd control debuffs