"Okay, everyone repair and head out to BRF."
"Dave's not here, man."
"What? Crap. Anyone know a tank?"
"Um, I know someone. He might be able to help, I think."
"What is he? DK, druid, warrior?"
"He's the Dragonborn."
"...what?"
GRUUL vs. The DRAGONBORN
So the question is simple enough: The Dragonborn of legend has faced incredible foes, like Alduin the World Eater, Miraak the leader of the Dragon Priests, and Harkon the Vampire Lord. He defeats ancient and legendary dragons every day, and can fight multipe giants or draugr death lords like it was nothing. could the Dragonborn of SKyrim realistically tank a raid?
FOr this discussion we'll be using:
A) An effectively maxxed-out Dragonborn of level 251, thereby having every single perk in the game, prepped and ready for this
B) Gruul, the simplest and most predictable boss in Blackrock Foundry. If you can't tank Gruul, you're probably not tanking anyone else, either.
SCALING
Translating between the two games requires a focal point. I decided on these two items:
1) Iron Sword, the first, and weakest, weapon you find in Skyrim
2) Longsword, a white-quality weapon that, based on its level of 21 and compared to Blacksmithing, is probably made of iron itself.
The base damage of Iron Sword is 7, and of Longsword is 15. Seven points of damage in Skyrim is fifteen in WOW.
DAMAGE/THREAT
If a tank can't hold threat, they're no good to the raid. We're not asking if the Dragonborn can solo Gruul, after all. There is no threat mechanic in Skyrim. A single-player game has limited need of such. But let's give him the benefit of the doubt with the same threat multiplier as any other tank in WoW.
That leaves damage. With every crafting skill at 100 and every perk in them, it's possible to make a dragonbone mace with a base damage of 63, the strongest customizable one-handed weapon in the game. 100 One-Handed skill with all the perks, maximized Fortify One-Handed gear and a potion on top of that, and you get a grand total of 376 damage. Factor in the damage scaling, and this becomes 807 weapon damage per swing. More, actually, because maces in Skyrim bypass some armor.
But now let's drop an enchant on it. Being a tank, he's likely bringing Absorb Health, and since effects like Slow and Paralyze won't work here, let's make the second effect Chaos Damage -- 50% each chance for fire, frost, and lightning damage. Again, with maximum skill, perks, a set of unique armor and a potion, you could get 34 Absorb Health and 42 Chaos Damage, which in turn, averages 63 per hit. Scale that up too, and you get an average magic damage of 274 per strike.
1,081 damage per hit isn't all that bad. It compares to 670 tank blade that Gruul himself drops on Normal mode quite favorably, which does 879.5 damage on average. The mace swings faster, but the Dragonborn doesn't get special attacks like Death Strike or Revenge. In any event, the damage is at least high enough to make holding threat realistic, just not necessarily trivial.
DAMAGE REDUCTION
If there's one area where the Dragonborn is exceptional, it's reducing the damage dealt. Since he's tanking, we'll load him up in heavy armor, and with his skills, he could easily hit the cap without doing anything drastic (such as using Alteration "skin" spells). But then there's blocking. Blocking in Skyrim is 100% successful on attacks that hit the shield, and they can reduce the damage in a multiplicative fasion. Upon hitting both caps, the Dragonborn will take 97.75% reduced damage from a blocked physical attack.
It would also be easy for the Dragonborn to craft and bring items that add both fire and magic resistance, hitting the cap for both of those as well. They, too, stack multiplicatively, so he takes 97.75% reduced fire damage, and 85% reduced nature damage (unless "being slammed by rocks" counts as "poison").
Combined, this makes the Dragonborn take far less damage from any one attack than any tank in the game.
COOLDOWNS
One of the Dragonborn's major issues in a raid environment is the lack of useful cooldowns. Racial and Standing Stone abilities have a 24-hour gametime cooldown, making them effectively useless here. That leaves Shouts, and most of them won't work on Gruul (as they don't work on dragons). Of note are Become Ethereal (8 second self-banish effect, 20 second recharge) Marked for Death (an armor reduction effect, handy for group damage) and Slow Time (which allows for flawless blocking).
CONSUMABLES
Another strength of a maxxed-out Dragonborn is their ability to make, and use, powerful potions. I'm not sure drinking hundreds of potions in one fight is that great of an idea, but making "flasks" of FOrtify One-Handed and Fortify Heatlh is pretty easy to do. In addition, the Dragonborn can bring Potions of Ultimate Healing, restoring all health instantly. Speaking of...
HIT POINTS
And now the bad news. Well, questionable news.
The Dragonborn starts at level 1 with 100 hit points, Each level from there you can put 10 points into Health, or Magika, or Stamina. Let's say this level 251 Dragonborn put points into health 200 out of 250 times, for 2100 health. The rest go to Stamina and Magika.
Add a powerful potion and enchanted items, and you get 500 more. Top that off with the Blessing of Arkay and end up with 2,625 Skyrim Health, or enough damage to take hits to the face, without armor or a shield, from that monster of a mace SIX TIMES. That's a lot of health as an abstract concept, considering most real life humans could take no more than 2 or 3 hits from a low-quality iron club before dying. This is Sunwalker Dezco's level of pain tolerance at a minimum.
But factored into WoW terms, it's 5625, or 6187 raid-buffed. Uh oh.
THE NUMBERS
Low on max health as he might be, the Dragonborn has enormous damage reduction. Gruul appears to melee for about 120,000 damage pre-armor in LFR, N, and H. The Dragonborn can block 100% of these, reducing the damage to 2,700 hit points. Two in a row, and the Dragonborn is barely standing. A third, and he dies.
So, can the Dragonborn tank a raid? Techincally, he already has. It was called Wrath of the Lich King, where most bosses would stomp tanks flat in three unhealed hits.
However, even the weakest healing-over-time spells anyone in your raid could cast will trivially heal the Dragonborn to full every second. Gruul will never kill the Dragonborn with standard melee attacks as long as you have even a half-assed healer on the case. If those attacks come spread out enough, Become Ethereal might help.
THE REALITY
Unfortunately for the Dragonborn, there's more to life than melee attacks. Even most blockable or magic attacks could overwhelm his incredible defenses and kill him. Take Inferno Strike and Inferno Slice. On LFR, the Strike does about 25% more than a melee attack, and is blockable. Assuming the other tank taunts quickly, the Dragonborn lives. However, on other difficulty levels, the Strike damage significantly increases. In Heroic, it does around 500-600k damage pre-armor, reduced by the Dragonborn's armor and shield to 12,375 (which is roughly double his health) and kills him instantly. Also, the Slice damage hits at the same time, denying even the 1 second any HoT would need to bring the Dragonborn to full health. Without a decent-sized group, Inferno Strike/Slash can easily kill him. And Become Ethereal, while a short cooldown immunity, takes 20 seconds to recharge, while Inferno Strike is cast every 18 seconds. Stacked external cooldowns would be required to save his life.
Other bosses won't be as forgiving. Unblockable physical damage, shadow damage, holy damage and Nature (but non-lightning, non-poison) damage are only partially reduced, 85%, so a hit for 40k WoW damage would kill him. Bleeds bypass all his defenses and would also almost certainly kill him.
It would be possible for the Dragonborn to tank a raid, but only on easily-predictable monsters, and even then, you'd be carrying him.