It's not hard, but mnk and Nin are not either. Drg is not hard, just extremely frustrating.
Okay...It has the shortest rotation of buttons and it just repeats infinitely in the same sequence of eight forever, it's buffs have absurdly long durations so there's no real fear of them falling off
Shortest sequence of buttons, but looking at strictly buttons to combo off of (no oGCDs)..
Nin has 6 ( no mudras)
Mnk has 6 (You practically can't even hit the wrong button since 4/6 will be stance locked)
Sam has 8 (no iajutsu casts)
Drg has 8 ( didn't count heavy thrust)
All these classes watch buff timers. Funny thing is, i think Nin and mnk can reapply mistakenly missed dots/debuffs (excluding the loss of GL3 or Huton which last over a minute and need less than 7 seconds to reapply or the cost of raiton so you can cast huton.) and miss out on less dps loss with their rotational combo alone. Comparatively speaking. Not 100% sure about that though, would be an interesting comparison though.
Also if Sam's buffs were any shorter, the would always fall off before you got to reapply them. Their GCD is only faster than Drgs, and skill speed isn't the greatest stat for Sam.
Edit: now that I think about it, I need to look into how good DH is for Drg in comparison to sam.
GL3 is passive, BotD is passive, Huton is passive (well all of them are practically passive). Meaning as long as you finish your combo in time, you get to keep it/you get more time. Almost but not quite to the same degree as Sam (do the correct combo, get your buff, finish it in time and you get to keep it.) All of the classes suffer when buffs fall off..it doesn't even have a persistent buff like GL3, BoTD, Huton, or Enochian, so it's more or less completely mechanics resistant. Kenki isn't even that hard to manage.
Sam looses damage and GCD speed.
Nin looses damage GCD speed.
Mnk looses overall damage and GCD speed.
Drg looses BotD (jump, SS damage bonus and GSM on 35 second timer AND eyes for some design decision flaws).
Not all the classes suffer the same.
Kenki is not hard to manage, but most people "just spend it". The only time you do that is when you're approaching surplus.
I'm not here to tell you Sam is hard or the other jobs are easy, people need to just take a step back and look at things objectively instead of subjectively.
Of course, for the sensitive people, this is how I feel and you all are entitled to feel how you feel. I'm just gonna have fun with the jobs.
Carry on.