What drew me into the MCH job was actually the heat blast into Gauss Round / Ricochet. It's a very nice combo action to use, and was really fun up to lv 60-70. Around lv 80, it's still fun, but it doesn't give off as much of an oomph when using it with wildfire compared to Drill and Air Anchor. The Heat blast combo is tough on latency too, but I think that's pretty much the gimimick of the skill - consecutive firing of skills nonstop for 7 seconds in "Hypercharge" mode. It makes sense you'd suffer a lot more under latency, but that's also a problem for all jobs with double weaving per 2.5 sec GCD, especially ninjas in their trick attack window since their GCD is much lower due to Huton and they have to double weave for 15 seconds straight, so that's a non-issue for me.

I feel a couple of changes that could make MCH feel better would probably be:

Wildfire does an exploding hit on the target marked for wildfire, and a 50% AoE splash damage on all targets in the vicinity. Make it really feel "explosive" since the damage doesn't compare as much to Drill or Air Anchor at a lower cooldown.

Air Anchor - also does its flat 700 potency damage, but also 50% to all enemies nearby, so it doesn't feel like you can't use a 700 potency attack and build battery gauge when you have a lot enemies to AoE.

Flamethrower - changing this ability to be more of a ground cone AoE kind of ability, set up a gun that shoots flames in an area for 10 seconds. Tagging a mob with Flamethrower gives a debuff to the enemy "On Fire" for 10 seconds.

Detonating wildfire on an enemy who has the debuff "On Fire" will double wildfire's damage.

Using Bioblaster on an enemy who has the debuff "On Fire" will immediately remove the Bioblaster DoT debuff and the "On Fire" debuff, but will do 1.5 times full damage over time of Bioblaster (maybe lv 80+ trait).

This way, Machinist's Lv 70 Capstone skill becomes cohesive with the kit rather than stand and wait until you finish burning everything down. I say 10 seconds for the debuff is a good amount of time since you would be able to setup a Flamethrower and immediately go into Wildfire, and for trash mobs, the debuff technically lasts for 20 seconds since Flamethrower will continually be refreshing the debuff on enemies as long as it's channeling (like AST's Collective Unconscious refreshing the Wheel of Fortune buff during channel). Ideally, you would want to use Bioblaster as it comes off cooldown during mobs to fit in a second Bioblaster in Flamethrower's duration.

The shotgun I believe will probably be upgrading Auto-Crossbow, so there wouldn't be major gameplay changes, but I could be wrong.