Riot's statement (as a recap):
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 be a pretty 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
I think the key part of it is this:
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
With that in mind, who follows that play pattern?
(at least old Malz, haven't seen enough new Malz to know)
These champions become far more useless with QSS in play, having to wait until their ultimate is back up to do much of anything and being restricted on who they can ult to get away.
The other champions you have listed don't lose a ton of their play pattern if their ult is removed, or people don't frequently get a QSS to deal with it.
removes all cc but it gets rid of a few peoples ultimates like lissandra 
where she freezes you and does dmg and you can keep attacking the enemy while they are frozen and if they use quicksilvers sash it just removed the ults perpose and I'm sure other champs have cc in there ults. I think the item should say removes cc unless it's an ult.
Champs with cc ults: lissandra
urgot (don't know if it counts as cc) 
Skarner 
Bard 
Malzhahar 
