RE: PokeBeach's Official X / Y Ban List
Thing is, MegaZard's greatest power is actually the fact that there are two forms, not one. While you can make guesses based on the opposing team's structure, they're not always accurate, and nobody guarantees your opponent makes teams with the same mindset as you. Banning one form of MegaZard will inevitably lead to the other's usage drop.
And while Charizard can 2HKO everything with the right set, it still doesn't mean that it's better. Talonflame fits in teams just as easy as Charizard, and both Talonflame and Pinsir carry STAB flying priority which makes them a huge threat. Talonflame can be countered by Zapdos, Rotom-W, Thundurus and Heatran. Mega Pinsir has similar counters. Apart from these, however, both are extremely annoying. Pinsir can wreck teams just as easy as Charizard (it has higher Speed, priority and Return/Frustration is stronger than Flare Blitz without the extra recoil as well). Talonflame is the bane of all setup sweepers in existence and the reason why prominent Pokemon of Gen V like Keldeo and Volcarona have seen very bad days. And while Mega Pinsir really only has one viable set, Talonflame has at least three, meaning it's also quite versatile.
So no. I think that right now there's nothing among these Pokemon that makes a ban needed. Aegislash is another story, with its unique style, raw power and defenses, so maybe that could be the next suspect.