Serious question about QSS:
Simply put, why doesn't it build into any AP items? Is there some sort of AP item equivalent that I just don't know about? It seems the two options are attack speed+MR(Dervish blade) or AD+MR (Mercurial scimitar).
It's called Zhonya's.
AD champions want to continue attacking to kill the enemy or sustain with their LS-> 
Mages want to wait for their CD while being safe for some time-> 
QSS has upgrades for AD and attack speed champions because they primarily rely on dealing sustained damage in fights. QSS lets them remove CC so they can continue to deal damage.
AP champions primarily deal burst damage and are reliant on their cooldowns. As such, they get Zhonya's Hourglass which will allow them to enter stasis and wait out their cooldowns after using their burst damage.
Item builds are another factor. For a long period of time, Zhonya's Hourglass was built on every AP champion at some point in the game due to how exceptionally useful stasis is. If we had an AP item building out of QSS, it would be a similarly essential purchase in most games if the stats we even somewhat reasonable for the gold value.
This is especially true for assassins/mobile champions. Imagine a champion such as Fizz with Lich Bane, Zhonya's Hourglass and an AP QSS item; how are you going to stop him during fights when he has two methods of avoiding CC (E and stasis) and one method of removing them (QSS)? He wouldn't even have to sacrifice more than a minor amount of damage to in exchange for being essentially immune to lockdown. Kassadin is a similar issues (with RoA instead of Lich Bane) since his R lets him avoid skillshots.
They should add it to Mikael's Crucible
I would not count non sr items with the caluation , I think it has to do with balance and type advantage (ap vs ad, ranged vs melee , mana vs energy vs reasoureless) on the balance part it would give galio an major boost in viability while hurting all mages and supports he have heavy cc like morge and malz.
On the type advantage it has to do with item the most common counter argument is why is there not an ad hourglass. Mages have item that good for them and ads has items that are good for them
I was about to create same thread just now! I partly agree with floraider42, even though in some games qss is way better than zhonya. On the other hand why isnt there any AD-zhonya? Anyway, mikael 's crucible stats are definetely not worth it for an ap midlaner, while Mercurial Scimitar has insane stats for any ad champ. I really hope in the major mage update coming soon, they consider revising mikael's, maybe splitting in 2 items: 1 for heavy ap (which will apply qss owner only) and one more supp-utility style like it already is(can target allies). P.S. the development/revision of qss on AP seems contradictory to new AD assassin item which is ruined by qss. I mean it hasnt even been released and they want people to try it out first. If it proves to be too strong then will be the time devs would make a change.
