That's what it is for me. I do dungeons of all flavors up to DLC hard modes. I do normal trials and Craglorn veteran trials. I do the group arenas. While I've only started to play the following build, this is the culmination of similar builds I've played in the past. It combines, for the first time, two diametrically opposed playstyles, a Brawler shielding build useful for lower end dungeons and carrying PUGs that have no damage, and a proper blocking tank. You can seamlessly change between the two playstyles without gear swap. Why would you want to? Because some fights in vet DLC and arena content also benefit from the Brawler approach. Why is this diametrically opposed to a conventional tank? Because a conventional tank blocks and has no use for stam regen, whereas the Brawler skill is a stamina hungry beast.
https://en.uesp.net/wiki/Special:EsoBuildData?id=477844
First of all this is a 5 medium armor build and we have 1.75K stam regen without a potion. That's a concession to the Brawler part. It comes from the Serpent mundus, the food, and one stamina recovery enchant. The next key ingredient are two Indeko cost reduction enchants, which are efficient compared to recovery enchants and regular cost reduction enchants. Brawler cost is reduced, Pierce Armor cost falls to 780, and Cinder Storm basically costs nothing. This means you can selectively combine the spammables with blocking while Cinder Storm won't encroach on your Unrelenting Grip sustain.
We're wearing two of my favorite sets. Tormentor ups the resistances of a medium armor build. It's medium armor for Brawler sustain, of course, but also for dodge rolling, which is normally so expensive on a tank. Resistances go beyond cap when you combine Hardened Armor, Resolving Vigor, Tormentor and the Master's 1H+S. Without the latter, they are just below. Tormentor turns Stampede into an AOE taunt and augments Unrelenting Grip to become a taunt as well. When a target can't be pulled, Unrelenting Grip becomes a free ranged taunt.
Steadfast's Mettle is possibly very underrated. It reduces block cost, dodge cost, bash cost and sprint cost. You might argue that other things are more valuable. If your agenda is to be a buff tank, then you would be right. This tank only provides Minor Brutality (Molten Armaments) and Major Force (Aggressive Horn). However a very low block cost, about 450 in this case, combined with Cinder Storm sustain - an Earthen Heart skill that returns 1K stamina on cast - creates magic. Did an Aegis, such as in Depths of Malatar or the final boss of Dreadsail Reef, ever eat up all your stamina while blocking? Well, now it won't. Block cost could still be lower - this is a compromise build after all - but a block cost below the usually recommended 750 makes these bosses easier. It also allows you to handle some serious aggro from trash pulls without running out of stamina. There is a particular trash fight in (normal) Dreadsail Reef where most PUGs wipe. They get overwhelmed. Not so, if you aggro everything with Tormentor, then perma-block while spamming Cinder Storm. For reference, you are charged the block cost every 1/4 second at most. To truly sustain perma-blocking, you would need a block cost of 250. This build doesn't quite have that. You still have to move, use synergies, potions and ultimates strategically. At any rate, I have found aggroing everything with Tormentor more beneficial for the group than wearing Pearlescent and you do need low block cost to pull that off.
I want to mention CP at this point. Blocking and resistances are your most important mitigations. Blocking and resistances have additive components. Resistances get you to 50% mitigation at cap. Blocking starts at another 50% and tops out at above 80%. The two factors are then multiplied together, which can yield a total mitigation of about 90%. Other factors, especially CP, are also multiplicative. 6% additional mitigation from Ironclad makes very little additional difference, but we use it for lack of better ideas. The rest of the blue CP go into damage buffs for Brawler. It's kind of the same story with the red CP. Bracing Anchor is a good buff at 20%, but it's multiplicative. Other blocking buffs are worth more. That 10% from being a DK and the 10% from Defensive Stance - a very underrated skill - are each worth more like 28% in actual testing that I did. There is a logic to that. It has to do with where those factors flow into the blocking calculation and the fact that they are additive with the 1H+S 20% block mitigation. This means that the DK passive and Defensive Stance are more powerful than they seem, whereas Bracing Anchor, while still good, is weaker than it seems. At any rate, I hate the movement penalty from Bracing Anchor. I opted for Bloody Renewal for Brawler spam sustain, much needed extra health, and the usual (for me) Celerity and Slippery. Love Slippery for when you can't see your character properly, whereas Celerity, medium armor and Steadfast's Mettle all help to keep up with a group that is rushing through a dungeon. Hate arriving at a fight out of stamina. That does not happen with this build.
Finally the skills. Pierce Armor speaks for itself. I only regret not having Caltrops as well, but realistically you help kill trash with that Master's 2H and everything is dead before you even have the Caltrops down. Pierce Armor is also your primary heal from Master's 1H+S. It being so cheap helps a lot with making it so, despite costing stamina. I deliberately avoided Coagulating Blood, because I find it far too expensive and only rarely useful.
Molten Armaments helps the group and helps our own damage while weaving Brawler.
Defensive Stance is purely passive. Despite not using Bracing Anchor, we have better block mitigation on this build than a non-DK in heavy armor with Bracing Anchor.
Unrelenting Grip - a pull is bread and butter for a tank. As discussed this is also a free ranged taunt for targets that can't be pulled.
Cinder Storm is mainly used as a stamina sustain skill. It basically allows you to turtle up and perma-block while spamming it.
I find Magma Shell more useful in really hard content, such as vBRP, than the customary Barrier. We're not very dependent on magicka sustain on this build, which Barrier would buff.
Brawler, of course, gives you a new shield every second you swing it. Some content, such as the final boss in vet Cauldron, is better done with Brawler than with a conventional tank. I've essentially soloed that fight on my Brawler stamsorc, e.g. finished it off solo in vet hard mode when the group died. The stamsorc has better Brawler sustain, though.
Inner Light gives crit for Brawler and balances out magicka between the two bars. The shield on the other bar has a magicka enchant.
Hardened Armor is bread and butter, of course. The damage shield is also nothing to sneeze at.
Stampede, as discussed, serves as an AOE taunt, due to the Tormentor set. There is nothing like being on the ball by using a gap closer (and a pull) for taunting. It plays so nicely.
Vigor is here as much for the heal as for the resistances.
Finally Aggressive Horn. Pretty standard.
PC EU: Magblade (PvP main), DK (PvE Tank), Sorc (PvP and PvE), Magden (PvE Healer), Magplar (PvP and PvE DD), Arcanist (PvE DD)
PC NA: Magblade (PvP and PvE every role)