It is not always an objective concept, that is correct. However, the consistently high numbers and constant evidence of the massive difference in DPS numbers is staggering. The fact of the matter is that if Samurai is constantly outperforming other classes, it's either really easy, or too strong. The average player can't even manage playing this game very well and I've seen players with weaker skill-sets perform well with Samurai. A BLM's difficulty has nothing to do with "being accustomed to casters," there were plenty of people who played SMN and/or healers who specifically avoided it because the skill ceiling for that class was so high in Heavensward. Also, Monk is hard to pick up and easy to maximize? I greatly disagree. Edit: (I just realized you stated that subjectively, but regardless.)
You say Samurai taxing, and your reasoning for this is...decision making? That's the hard part about it? A bunch of what-if scenarios of mostly meaningless conjecture that only happen at certain moments? The whole reason Monk is so difficult is because unlike Samurai if you lose your greased lightning stacks your damage takes a massive hit. You have to regain your stacks all over again. Right now Monk only has two buttons to properly restore their stacks, one of them being on a 60 second cooldown (which requires you to get hit AND take yourself out of DPS stance, a DPS loss) and another on a 3 minute one. You are arguing from a sheer dummy standpoint. Managing mechanics on a Monk and keeping your stacks up, while keeping your buffs up, in order to keep doing the most damaging parts of your combos, is the optimal way to play. If you keep having to constantly apply Twin Snakes and Demolish more than you're doing Snap Punch and True Strike, you're doing poorly. Being able to weave Forbidden Chakras at any point in your combo if you get lucky with crits or brotherhood, a function that purely relies on RNG. Fact of the matter is, Monk play is more reactionary, and Samurai play is based around decision-making. Like you said, the difficult is dependent on the user, but I don't really see that many strong Monk parses, do you?
The worst thing that can happen to a Samurai is that they have to decide positives and negatives. That means people who have a calmer thinking process can play it easier. A lot of people cannot play on reaction either because they're simply not good at it, or they may find it too difficult for their own reaction times. It's partially why some people play FFXIV, the GCD and combat speed is very slow in this game. Monks directly contradict that, having the fastest GCD casting in the game and having a mechanic that requires you to have as much uptime as possible. If it was so easy to master I would see far more advanced monks in any portion of this game's lifespan, and I haven't. Meanwhile I've seen more Samurai than I've ever seen Monks performing very strong DPS and high levels.
As for buffing vs nerfing, I agree with this yet again. I just don't trust Square Enix. I'm always an advocate for buffing other classes over nerfing specific ones. I just don't trust SE to do it properly. I would rather not read in a few months complaints from Samurai players about how DRG, MNK or MCH was overbuffed and they bring more utility + damage than them.
As for SAM's identity vs my job's, I couldn't care less. My only 70 class is Red Mage. I just personally think SAM is too strong compared to the other classes with very little risk involved. Nothing SAM does influences my class' position in any sort of hierarchy, and my class works well with it. I didn't like WAR in 3.0 either.