Evaluating the various potions for Tanking vs Threat:

Earthen Potion
= 4800 Armor = mitigation = can be equated to mastery (1 armor = 1/7 mastery rating)
= 685.714 mastery rating = 3.8247 mastery skill = 8.605575% to Prot Paladins (*overstated slightly)

Golemblood Potion
= ~~1200 Strength = 300 parry rating = 1.6976% parry~~ (pre 4.2)
= 1200 Strength = 324 parry rating = 1.8334% parry

Potion of the Tol'vir
= ~~1200 Agility = 3.940% paladin dodge~~ (zero dodge to plate classes)
= ~~1200 Agility = 2.786% warrior/DK dodge~~ (source) (zero dodge to plate classes)
Agility increases dps via crit. Which works out to about 50% the value of Strength to prot Paladins.

So that results in the following in terms of {Tanking --> Threat} tradeoffs, potion order is:
Tanking -->
Earthen Potion
~~Potion of the Tol'vir~~
Golemblood Potion
Deathblood Venom (highly situational)
<--Threat
Druids have an easy decision. Potion of the Tol'vir clearly wins on both tanking and threat for bears.

* Temporary armor bonuses (Earthen Potion) are not multipled by talents, meta gems or other similar effects.
Therefore the standard conversion of {1 armor = 1/7 mastery rating} will be slightly off and overstate the value of the armor potion.

EDIT: updated for 4.2

Комментарий от 6454

The Cataclysm mitigation potion. All of the +armor potions can be obtained from the following wowhead filter: Consumables: Potions: Armor>1

Комментарий от 385492

I wasn't really using a potion at all recently while tanking, and I thought this might be a viable option to carry a stack. I crunched a few numbers and this is what I got. Feel free to correct this if you feel the need.

Using the armor damage reduction formula found here:
DR = Armor/(Armor+2167.5*LVL+158167.5)
One can find that your gain in damage reduction from this potion can be described by:
%gain = 100(Armor+4800/(Armor+4800+2167.5*LVL+158167.5) - Armor/(Armor+2167.5*LVL+158167.5))
Simplified in an algebraic calculator for level 85's:
%gain = 2607000/(Armor+26070) - 2607000/(Armor+30870)
This leads to a outcome of about 2.5-3.25% gain in physical mitigation for plate tanks. It's not outstanding, but at least noticeable when used in conjunction with other cooldowns, etc. As a Pally, I'm likely going to macro this into my Guardian or ArdentD macro and investigate its worth.

Комментарий от marmars

Quite possibly the least desirable item to find in your Сумка с таинственными экзотическими вещами

Комментарий от Avante

This is now the replacement/reincarnation of the Зелье несокрушимости . If you have any Зелье несокрушимости's left, put them on the AH, and they will be converted to Зелье земельников instantly. Note the stats change :)

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Уровень предмета: 85

Требуется 80-й ур.
Использование: Усиление брони на 4800 ед. на 25 sec. (1 Мин Восстановление)

Максимум в стопке: 20

Цена продажи: 50

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