I had no idea there was such a thing as faulty facts and numbers. It doesn't seem like you enjoy DRK at all. You've put on a convincing performance, I've been fooled! Still, this block of word vomit has been quite the task to dissect. But let's start:
I don't quite understand what you mean "letting us do what we already did." You couldn't BS/Quietus before the gauge, nor could you extend your buffs. If you mean we were already doing damage, then the gauge allows us to do more. By definition, literally, this is what it means to augment a kit, and the gauge performs that exact function. In dungeons, this gauge allows us to continously AoE, indefinitely. We sure as heck couldn't do that before the guage. Also, who cares when we get our guage? Anything before cap lvl is irrelevant to judging a class.
Think about our most-used skills. SE, C&S, SS, and BS. All their DA effects solely increase damage, which makes the first question sound oblivious. As I've said before, the prescence of quietus and the interaction it has with our MP and gauge allows us to AoE forever. As for quietus's MP regeneration, why even bring it up now when it hasn't been a relevant issue since patches ago?
Sure, we could streamline BS's description to say it's unaffected by tank stance, but not something I'd bring up as a keypoint as to why "DRK has faults!" Why is Inner Release locked behind the lvl 70 job quest? That's the whole point of WAR's identity, especially since 4.2 "Berserk" outright sucks. "No other job," eh? You forgot to look at your fellow tank! It's just our capstone and there's nothing wrong with having it at cap. But either way, leveling doesn't matter because 99% of our time is spent at cap lvl.
Because DRK's gameplay is about resource management. It's a wonderful thing to appreciate when you actually understand the class. You can turn your MP into mitigation, which in turn gives you another resource for damage. The way you structure the question seems like you want some sort of intricate interaction with the gauge and the guage itself. Neither PLD nor WAR have this going on. In fact, all PLD gets from its gauage is sheltron and intervention. WAR just does what it's always done, except now you add upheaval and onslaught.
How much time do you need to learn a mechanic? Again, you spend far more time at cap than you do leveling. You have all the time in the world to learn how to use your skills. It's the same growing pains other classes go through as well.
Becuase you're encouraged to use your primary combo. WAR essentially uses two combos only, but even then it's just a one button difference. I'm not sure you can call a single button difference an engaging choice. TBN is a utility becuase it saves your healers having to worry too much about you. It's utility because it can be used for fluff damage, tank busters, or raid-wides alike. It isn't tied down to a gauge or stance either, like sheltron or inner beast respectively. It can be used on party members as well. There hasn't been a fight that outright requires raid-wide shielding. In that respect, it's utility enough. I've said it before many times, but to say TBN cost a resource is faulty when you've given damage equal to the cost of a DA. Again, the point of DRK is simply not to overflow. If you find yourself needing TBN and not being able to "becuase it cost a resource," you've managed your resources poorly. That said, TBN is essentially free mitigation on a 15 second timer.
That's what resource management is all about. That's what the job is. This is a clear case where if this an issue for you, then it's not so much a fault with the job, but maybe the job isn't for you.
Because you don't communicate with your party.
Gee, why is equilibrium heal locked behind a stance? Do you really need a heal from your main damage combo? PLD doens't seem to.
Because DRK is fine.
My case is not relying on one encounter/instance/clear (despite it being several), but pointing out DRK holds no one back.