Warrior has the most cooldowns though.
Don't sleep on Raw Intuition. You can throw that down between basically each other CD and be good to go.
Otherwise between Arm's Length, Rampart, Thrill of Battle, and Vengeance, you've got coverage for fucking days. 70+ DRK is the easiest to just meme your way through dungeons, but warrior is right behind imo, and warrior can do it from early levels since all those cooldowns are quite low. Nascent Flash is nice, but raw intuition is almost as good and you get it at like, idk sub 30.
As far as 'when' . it's the same on all the tanks: Rotate them until things start dying. If it's a big pull, the bigger ones earlier are better, if you're pulling less or have multiple pulls back to back, I'd just do rampart/arms length, but usually if you're not using them, it means you cna pull more.