Since nobody has yet I'll give calcs of Altaria vs. Mega Zard X and Y:
252 Atk Tough Claws Mega Charizard X Flare Blitz vs. 252 HP / 252 Def Altaria: 108-127 (30.5 - 35.8%) -- guaranteed 4HKO after Leftovers recovery
0 SpA Altaria Draco Meteor vs. 4 HP / 0 SpD Mega Charizard X: 240-284 (80.5 - 95.3%) -- guaranteed OHKO after Stealth Rock
252 SpA Mega Charizard Y Air Slash vs. 252 HP / 4 SpD Altaria: 136-162 (38.4 - 45.7%) -- guaranteed 3HKO after Leftovers recovery
252 SpA Mega Charizard Y Fire Blast vs. 252 HP / 4 SpD Altaria: 99-117 (27.9 - 33%) -- 88.6% chance to 4HKO after Leftovers recovery
0 SpA Altaria Draco Meteor vs. 4 HP / 0 SpD Mega Charizard Y: 93-111 (31.2 - 37.2%) -- 79.4% chance to 3HKO
That is quite impressive walling of the Mega Zards, and Altaria can even OHKO Mega Charizard X with no investment at all! Unfortunately she's too weak to hurt Mega Zard Y, but she can still toxic stall him out.
They have been posted multiple times no? I believe it was a key factor that helped push him to win (as many had distinctly said, "Lets get a true Char counter").
He does not. The only thing he can do is toxic stall. really nothing else. The only move he has that can actually do decent damage in this metagame is Draco Meteor. That's always an option. He also does not have any moves that have a significantly high chance to spread status, so toxic stall is the only thing he should mainly be used for.
Ah, that is disappointing. If only he had a way to get a double status or so off then.