Fantastic! Actual data, let's dig into it and get some proper numbers!
All of these stats are fully raid buffed.
Pre raid gear: Warrior, 8409 health, 8055 armour for 59.4% damage reduction, Druid comes in at 1072 health and 11838 armour for 68.3% damage reduction.
Over a 6min fight, the warrior took 199614 damage, with an average of 1348 damage per with and a maximum of 3094 damage.
The druid took 235870 damage, 1254 average hit and 2776 maximum.
So for pre-raid gear, the druid takes lower hits overall, but looses out in overall damage taken by around 18% i believe due to lower overall avoidance.
T1 gear: Warrior has 10708 health, 9302 armour for 62.8% damage reduction. Druid comes in at 11574 health, 12515 armour for 69.5% damage reduction.
Over a 6min fight the warrior took 211028 damage with an average hit of 1370 damage and max of 2860 damage.
The druid took 186375 damage with an average hit of 1187 damage and a max of 2416.
So in T1 gear, a druid has more health, takes smaller hits, and averages less damage taken overall.
T2 gear: Warrior has 13522 health, 10400 armour for 65.4% damage reduction. Druid comes in at 13957 health, 13478 armour for 71.0% damage reduction.
Over a 6min fight, the warrior took 137749 damage, with an average hit of 1138 damge and a maximum of 2834 damage.
The druid took 204412 damage, with an average hit of 1209 damage and a maximum of 2408.
So in T2 gear, the druid takes smaller hits overall, but the warriors avoidance kicks in and saves in a whopping 48% damage taken.
T3 gear: Warrior has 14646 health, 12332 armour for 69.2% damage reduction. Druid comes in at 15186 health, 15286 armour for 73.5% damage reduction.
Over a 6min fight, the warrior took 98935 damage, with an average hit of 810 damage and a maximum of 1720 damage.
The druid took 191524, with an average hit of 1107 damage and a maximum of 2298 damage.
And finally in T3 gear, the druid falls behind in all categories, he takes 94% more overall damage taken and the individual hits are on average higher aswell.
So with the gear used in these tests, the warrior becomes the winner in all categories in full T3, with every conceivable buff, cool.
Now let's list all the reasons this data is kinda misleading.
1, This is private server data.
2, Incorrect gearing options for the druid, even in full tier 3 he's not armour capped, something that can be achieved in blues, showing a clear lack of knowledge of how the class functions.
3, All testing was done against a boss (Sulfuron Harbinger) with relatively weak melee hits, something that heavily favors Warriors.
4, Every buff known to man was used, and the stats themselves are highly dubious, this warrior is competing statswise in his T1 with Kungen while he's progressing Naxx 40, this being on a private servers makes all of these numbers highly suspect.
5, Far too small sample size to be statistically relevant, even between the different factions samples, Alliance vs Horde Warrior tank in almost the same gear, in some cases here the damage intake varies by 20-40%, same thing happens with the druid in multiple samples.
But even IF we grant that these numbers are accurate, all this data shows is that Warriors are more mana efficient to heal than a Druid, someting we already knew.
So let's go over your statements.
1, Druids take almost twice as much damage as warriors. -In terms of overall damage, in T3, yes, If we compare average hits it's 810 damage vs 1107 damage on average... not exactly a mindblowing difference.
2, They take damage in a much burstier fashion. -This is very true, Warriors are the kings of smooth damage intake.
3, Your druid tank will be a huge drain on your healers. -Eventually in T2 and T3, yes a druid will require far more healing. But when progressing Onyxia/MC and BWL, not so much, and again, this is with a very poorly geared druid, what kind of druid doesent armour cap? Going from 70% to 75% damage reduction is an effective 20% damage reduction. (math example, 1000 unmitigated damage, 70% brings it down to 300 damage, 75% brings it down to 250 damage, 250-300 is a 20% difference.)
4, Assuming he doesen't straight up die to a streak of 2 big hits. -Complete nonsense, even factoring in crits, the statistics you yourself linked shows that the largest hits a Druid -ever- take, are comperable to those taken by a warrior. Any hits that can 2 shot a Druid, will also 2 shot a Warrior, even factoring in Crits on the Druid and regular Hits on the Warrior.
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Again, i have to stress that -NO ONE- is arguing that a druid is a better tank than a Warrior, simply that it absolutely CAN be done.
It's not optimal in any way, but it is certainly not impossible or something you would have to force your way through with sheer stubbornness.
Here we have a video from 2006, showing a druid main tanking Chromagus in BWL during progression.
https://www.youtube.com/watch?v=H6zijYqbves
So after all this, all we have conclusively shown, is that a Warrior is a more mana efficient tank, wich again... we already knew.
It's a far leap from being draining on the healers, to being unusable.
- - - Updated - - -
Please read through the last 2 pages or so where we go over the math of proper tanking and show where the math is done incorrectly and druids become unable to tank.
This is being discussed because people have preconceived notions about what can and can not be done in Vanilla that have been around for about 14 years now, it's sheer ignorance, propagated by people who never actually do the math but insist on spreading this misinformation through sheer hearsay
And again, -no one- is arguing that a Druid is as good or better than a warrior, simply that it absolutely CAN be done.