I don't understand how Garchomp is more viable than Mega Heracross. Sure, the two do completely different things, but but at the end of the day Mega Heracross is the better pokemon and at worst should be in the same rank as Garchomp. Garchomp faces immense competition in all of its sets, and in my opinion, none of its sets are all that great. Its scarf set is outdone by Landorus-T, lead sets are (arguably) done better by Mamoswone and Terrakion, and the SD wall breaker faces a ton of competition from most megas. That and the fact that both of its STABs, while good, suffer from having plenty of immunities. Most teams have at least two ground immunities and usually one dragon immunity. All of these reasons are why Garchomp belongs in A rank, and most certainly not above Mega Heracross. Mega Heracross, like Garchomp, faces competitjon too. However, of the mega wall breakers, Mega Heracross is generally accepted to be the best (also just realized, wtf is Mega Gardevoire doing in A+???? Mega Cham and Mega Heracross are better than this...not gonna get into that right now though) in its role, unlike Garchomp who isnt really the best at any of its roles. Mega Heracross has good coverage and high base power moves that can go through subs and can often land a timely crit. Its middling speed isnt really much worse than Garchomp's (or any of the other mega wall breakers) due to the lack or notable threats inbetween them. On another topic, Garchomp and Azumarill being in the same rank is even more of a crime than Garchomp being above Mega Heracross. Again, the two dont really compete for a team slot, but Azumarill is a much better pokemon all around and shouldnt be in the same rank as Garchomp for the reasons already stated.
tl;dr Mega Heracross shouldnt be a rank lower than Garchomp, Garchomp shouldnt be in the same rank as Azumarill, and Mega Gardevoire shouldnt be above Mega Medicham or (especially) Mega Heracross. At the absolute worst, Nega Heracross is in the same rank as Garchomp and Mega Gardevoire. It is nothing short of a crime for Mega Heracross to be a sub rank below. Maybe stall teams adopted to it slightly, but stall teams arent even that common to befin with in a metagame filled with offense and that still doesnt change the fact that Mega Heracross is better than some of the A+ poke on.