Not to be a downer, but this is a team dump with a couple lines and low ladder replays.
As for the team, as already pointed out by
AnybodyAgrees, Imposter is an MVP against this kinda team. Kudos to you for making 37 with a team weak to the biggest threat in BH. You could actually solve this issue pretty easily, simply make Chansey fur coat and give it a Shield move. You probably have to ditch Dark Void though. Giratina should be able to wall Blaziken, and Fur Coat Chansey would wall Mega Mewtwo Y and Mega Rayquaza.
And while priority Mega mewtwo y sounds cool in all but well
252 SpA Mega Mewtwo Y Tri Attack vs. 252 HP / 4 SpD Mega Audino: 97-115 (23.6 - 28%) -- 90.2% chance to 4HKO
252 SpA Mega Mewtwo Y Tri Attack vs. 0 HP / 0 SpD Mega Rayquaza: 119-140 (33.9 - 39.8%) -- guaranteed 3HKO
Tri Attack is horrible coverage. And there is no way around that. There are so many things this MMY set can't even hope to touch. Registeel, Giratina, Chans, Mega Audino, Lugia, Hoopa-U, Regirock, Tyranitar, all easily switch in and the list goes on. Considering Protean sets are generally considered to have no 1 reliable answer, you are giving up quite a bit for priority Dark Void, Parting Shot, and Tri Attack.
Giratina should probably be defensive. Defensive helps it take on Protean MMx, Primal Groudon, Mega Aerodactyl, Ho-Oh, and a few others. Most of the common special attackers (MMy, Mega Gengar, Mega Ray, Diancie-Mega,) beat you anyway.
Mega Blaziken is generally outclassed by Mega Mewtwo X.
252 Atk Mega Blaziken V-create vs. 4 HP / 0 Def Arceus: 294-346 (76.9 - 90.5%) -- guaranteed 2HKO
252 Atk Mega Mewtwo X V-create vs. 4 HP / 0 Def Arceus: 224-264 (58.6 - 69.1%) -- guaranteed 2HKO
Yeah V-create is stronger by quite a bit actually, but every other hit is stronger and MMx is faster and bulkier. If this was a set primarily dedicated to spamming V-create (say tinted lens or prank copycat), Mega Blaziken is certainly better in those cases but here its generally worse.