I'm sorry to say "it is too early" but that is how I truly feel at this point. But I will give my opinion as I have already reached 58MCH.
I do not wish to complain about DPS just yet. I don't use a parser so I can only tell from eyeballing things and watching closely. So far I have seen MNK and NIN do wayyyy more damage than me. Like, approaching double the kind of damage I do. I'm not sure if that's balanced or not, as I like being able to attack from a range. It is expected for melee DPS to outdamage ranged DPS. It makes logical sense. I haven't come across any good DRGs yet (just a bunch of Estinien wanna-bes) but I would assume that good DRGs can outdamage MCH like crazy too. Anecdotally I seem to be outdamaging BRDs, although it's quite possible that I've just been playing with bad players.
Little side story, I strugged on Bismarck with a party of 2 BRDs + 1 MCH. We did not pass the DPS check on the adds and wiped several times and our party disbanded. After requeuing I ended up with the same 2 BRDs and we still had a difficult time. Incidentally I also had a failed party at Dravana that consisted of 3 MCHs (2 of them stayed in GB the entire time while I scratched my head wondering if that was the right thing to do, we ended up running the timer down and failing the duty).
Another anecdote, I just finished leveling SMN to 50 before the expansion came out. I don't like casters in this game, and I had preconceptions that SMN was the laughing stock of the game. I'm sorry to say that actually playing the class and giving it a fair chance only confirmed my suspicions. Because of my poor experience with this I've had more patience for MCH. I don't know what SMN is like post-50, but from my experience 30-50 MCH is better than SMN. You can complain about Split Shot all you want, but I still much prefer it over Ruin (and Ruin2 also!!).
One weird thing about MCH is the 1-2-3 combo, which doesn't exist. It's more like a 2-3 combo when you have ammo. Then when you don't have ammo, it's like "spam 1 and pray for a 2 proc. Then when 2 procs get down on your knees and pray even harder for a 3 proc."
Personally I'm still getting used to Gauss Barrel. I knew there was gonna be problems just like BRD is experiencing problems with WM. To me I find it strange to come across many other MCHs leaving GB on all the time. For me, I have it off way more than I have it on. It's like I don't even want to use it unless Rapid Fire is also up. No one's complained about my damage yet (reached lv58, farthest I've completed is The Vault). In fact I've picked up quite a few commendations which is rare for a DPS. Grenado Shot is super awesome and even Spread Shot is pretty cool with a nice sound effect and has its uses. I only got talked down to once by someone who was surprised that I wasn't spamming Blank and knocking everything away... I'm sorry if people have had bad experiences with this but you shouldn't automatically assume everyone's gonna do it...
No defensive cooldowns is an issue. Not a problem, but an issue. Second Wind is a great cross class skill to have that Machinist is missing. Every good Bard has always used this. It's an issue because if the rest of your party isn't playing well there's nothing you can do about it, whereas on other classes it's possible to pick up the slack and take a few hits. Machinist cannot take any hits outside of unavoidable / party-wide AOE damage. I have never used so many X-Potions in my life until I started playing Machinist. Glad I made room for another hotbar in my UI before the expansion came out! I think it's not a serious problem because MCH has a bunch of tools, personally I have found some of the skills to be super valuable. For example Foot Graze + move out of range and attack a different target is a very useful strategy. You can even Lead Shot them first and then bind them after, and they can still take that DOT damage without losing the bind. Blank + Leg Graze + kite is also extremely effective versus single targets. I have fought monsters that if I stand still they bring me down very low (even to the fear of death occasionally), yet if I fight the same targets and kite them I can defeat them with taking little to no damage at all.
The tools are there, you just gotta know how to use them and when. One of the tools though, Suppressive Fire, isn't that great. Before the game came out, I thought to myself "Wow, MCH has stun, silence, slow, bind. That's so overpowered! Ranged stun? Too godly!" Now that I'm actually playing it, I was disappointed to find Stun + Silence using a shared cooldown. To add insult to injury, Suppressive Fire is melee range only, making it have very limited uses in a party role. Think of it this way, as a ranged class, you're expected to fight at a distance. That means you should be out of range of the stun for most of the fight. That means to cast the stun requires movement to get in range. But your movement is limited by Gauss Barrel, where the more you move, the less damage output you'll have. I find myself using the Silence WAY more simply because I can cast it at a range. It's not cool that the stun shares a cooldown timer AND is melee range... They should pick one or the other, with both I almost never use this in a party.
There are some issues but I'm sticking with MCH for now. I hope to reach 60 and complete the storyline in the next day or two. So far I haven't ran into any problems that made me want to quit playing MCH.