Can we drop this idea that dropping your tank stance makes you a good tank? It's bullshit, and not something people should strive towards when they're still learning the job. Your number one job as a tank is to keep things hitting you. Dropping your tank stance is antithetical to this.
"But DPS!"
You are a TANK. You're not a Dragoon. You're not a Ninja. You're not a Monk. You're not a Samurai. Your job is to focus enemy damage on yourself and survive it. If you want to do better DPS, go play one of those jobs. Tanking well means minimizing the chances of losing threat, and minimizing the chances of dying.
It doesn't make you somehow better if you like to play more dangerously. It makes you a liability. Yes, maximize your damage output (because that's how mitigation in this game works), but don't do so at the cost of making it easier for you to lose hate. Say you have a SMN who, after using Quelling Strikes on their first Dreadwyrm Trance, gets a lucky string of crits while setting up their second. While you're sitting there with your stanceless sea urchins, the mobs (except for your main target) all turn away and nuke the SMN before either you or the healer can react.
Also, yes, I do DRK. It's quite fun when PLD gets boring and my FC healer claims to be too tired to heal me on WAR. But in my experience in sitting next to said healer, DA-AD doesn't heal for anywhere near enough to be sustainable (even on big pulls). Almost invariably, I hear from her how I'm being hit really hard, even when I do exactly what you're doing. I'd challenge you, next time you're in a dungeon, to ask your healer to only use Regen on you while you're doing that and see how long you last.
Of course this also is a symptom of the fact that healers in this game are way too powerful for the amounts of damage that mobs put out. There is almost no consequence for this type of reckless playstyle, because healers can usually just heal through the damage anyway, with almost no downside.