First of all, 6gcd Wildfire is impossible without memespeeds (2700+ sks), second off all, 6gcd OH is impossible when overheating with a gcd (OH doesn't apply to the gcd used to initiate it).

The problem with MCH is Flamethrower. It's annoying to use and far too tight with the timing for the general population. It enables 6gcd overheats which, in my opinion, shouldn't be a thing because of the latency disparity between players. It's also counter-intuitive for AoE now that it overheats halfway through the duration. Another personal gripe I have is forced ogcd weaving during Rapid Fire which is caused by the tight OH/WF window, it's cancer especially for high latency people. Ogcd weaves during Rapid Fire have zero room for latency (gcd anim lock + ogcd anim lock = 0,75s + 0,75s = 1,5s = gcd during RF) which is even tighter than double weaves during normal gcds (0,75s + 0,75s x 2 = 2,25s < 2,5s base gcd) and even those can be a pain for people with high ping.

For MCH to actually feel comfortable to play for more people:
-Flamethrower needs to not be stupid or there needs to be another way to OH or OH needs to be a penalty instead of a gain.
-The OH/WF window needs to be longer or Rapid Fire needs to not be a thing or there needs to be less weavable ogcds.

But those things bring their own problems with them so I doubt MCH will get any adjustments. Their dps is fine so obviously they don't need any changes. ¯\_(ツ)_/¯