I had heard of this possible suspect, who is now unfortunately become reality. I have already made an idea about the possible ban, so here some thought.
Aegislash was the most awaited pokemon of XY, why? because is the first pokemon capable of checking/countering Terrakion (especially Choice Band set) in OU scenario;with his incredible Ghost/Steel typing he s also a good check of many Offensive threaths of the metagame that otherwise would be seen everywhere, it is, for example, a good answer against Mega Medicham, Mega Gardevoir or Hawlucha, while air baloon gives it the possibility to check Mega Heracross and also counter some ground type such as Gliscor, Excadrill or Diggersby. With the effective ban of both Deoxys forms Aegislash s ability to enter almost everytime on Chansey makes it one of the few pieces in the hands of offensive players who have to face a metagame increasingly based on the use of stall teams. I personally don t think that Stance Change + King's Shield combo, considering Aegislash weakness to Ground/ Fire typing (Garchomp, Excadrill, Charizard X/Y and Talonflame are all top 10 usage) , opens more 50/50 scenarios than other mons like Bisharp or Mega Mawile. The difficulty of Countering/Checking him is maybe the reason for wich some player consider it "broken" and for wich Aegislash is under suspect, most common switch in such as Heatran, Diggersby, SdefGliscor and Mandibuzz can be pulled down easily, in fact running LO full speed it can 2hoko Heatran on entry with Sacred Sword, Running baloon, as I already told, it can check Ground types, while(quite inusual) Head Smash basically allows him to Hoko Mandibuzz after Stealth Rocks damage.
Probabily after laddering i will have more clear ideas, but right now I think that even if it totally centralise the metagame, it guarantees a good equilibrium in this metagame too and therefore deserves to remain in OU, at least, i don t really think it deserves to be banned more than something like Charizard