Ignoring the fact Dark Knight has the strongest mitigation suite, if you're in a casual group then it literally doesn't matter what you play. You already have the whole told equalizer of gear. So play whatever you enjoy. Frankly, I find more than a little silly you're insisting Dark Knight is terrible to play because it can't match Warrior in dungeons? Who cares? Seriously. They're dungeons. Not only are they so pitifully undertuned nowadays tanks can solo them (yes, even DRK) but Dark Knight is far from the only "unbalanced" job in a dungeon setting. How does nerfing Bloodwhetting suddenly make Dark Knight more fun? I'm not even against that either but if you put your enjoyment solely on how good a job is relative to its counterparts. That's on you then hun.
And just to comment on the buffs response. Unless you're group is running a purely selfish comp, Dark Knight still benefits more from raidbuffs than any other tank. Likewise, it's the strongest tank in TEA. Yes, it doesn't hold up well in the 70 Ultimates but that's SE being silly with ability distribution.
The fact you say this when 6.2 into 6.3 was the most aggressively overtuned Dark Knight has ever been speaks to how you only care about it being the best and little else. As I said, the job wasn't good, it was oppressive. You're seriously going to argue Dark Knight having more clears of Omega than every other tank combined "struck a good balance"? Come on. If you don't want to play Warrior, don't. Play the job you want. It quite literally doesn't matter outside of very early prog. Even in said prog, it doesn't necessarily matter. My group week 1'd with a Red Mage.
Unfortunately, with how Dark Knight is designed, it simply can't be the strongest tank without dwarfing the other three. It plays too well in the two minute meta and essentially gets free resources whenever there's downtime. They would need to overhaul a lot of Dark Knight's current design to address that, which may not being to your liking. Alternatively, maybe they give enough to the other tanks to balance out their burst phase. We won't know until Dawntrail but simply cracking up Dark Knight's number isn't the answer unless you just want to be the strongest tank.