Rune forging tank

I have read on the sticky that sword shattering (the rune with 4% parry) is better than stoneskin gargoyle. I cannot understand why

Could someone explain to me please ?

Thanks!
Anyone plz?
For tanking parry dodge and mastery have higher priority than stamina.
Lets say a boss hits for 100k every 2 seconds before any reductions.

4% parry makes you(before factoring DR) take 4% less damage.

4% armor increase decreases the physical damage you take by not even 1%.
2% stamina will increase your health by roughly 3k. Stamina's benefit is limited to increasing your minimum DS heal (here roughly 210), and allowing you to survive successive large hits. Because of the DS nerf sitting @ 15% soon, the need for more stamina (including those that gemmed it for HM's) is diminishing.

Essentially it boils down to 4% less damage taken (again, before DR) or less than 1% damage reduction, & 1/500(made up statistic in an attempt to convey its ineffectiveness) chance to be saved by the extra stamina.

Edit: another way to look at it: 4% parry = ~700 parry rating(14 epic parry gems)
3k hp (2% stam) = ~225 stamina(3 epic stamina gems)
My point here is - even if you wan't more stamina, it would still be better to keep the parry runeforge & gem more stamina.

Lets say a boss hits for 100k every 2 seconds before any reductions.

4% parry makes you(before factoring DR) take 4% less damage.

4% armor increase decreases the physical damage you take by not even 1%.
2% stamina will increase your health by roughly 3k. Stamina's benefit is limited to increasing your minimum DS heal (here roughly 210), and allowing you to survive successive large hits. Because of the DS nerf sitting @ 15% soon, the need for more stamina (including those that gemmed it for HM's) is diminishing.

Essentially it boils down to 4% less damage taken (again, before DR) or less than 1% damage reduction, & 1/500(made up statistic in an attempt to convey its ineffectiveness) chance to be saved by the extra stamina.

Edit: another way to look at it: 4% parry = ~700 parry rating(14 epic parry gems)
3k hp (2% stam) = ~225 stamina(3 epic stamina gems)
My point here is - even if you wan't more stamina, it would still be better to keep the parry runeforge & gem more stamina.

That's a lot more clearer than the sticky explanation. Good job.
Thx for explaining this to me. Now I understand the importance of it and will regorge as that
Still not sure if it will take priority on HM's as the dmg and hp debuff is only for normal, so SSG may still come out on top for HM. As for reg, yes, SS > SSG.
SS isn't affected by the DR.

SS provides roughly 6-7% relative damage reduction.

SSG provides roughly 2%. The maximum HP you get from SSG caps at about 5k in full i410 gear, using 2x stamina trinkets, gemming every single slot with stamina, and with the +10% HP from a shaman. That's pretty pathetic, considering a stamina trinket by itself gives 3x as much stamina.

As for how those relative damage reductions are calculated, basically you compare the damage you're taking now with the damage you would take afterward.

SSG should give you about a +1% (additively) increase to your damage reduction from armor. Compare the sizes of the hits that you would take, or, in an expression

Reduction = 1 - (1 - %DR_SSG) / (1 - %DR_No_SSG)

I'm not going to calculate that value for your gear specifically, but I 100% guarantee you it is within 2.0-2.6%. In simpler terms, what that means is if you use SSG, every single hit you take will be 2.0-2.6% smaller than the hits you are taking now.

Similarly, with SS, what you need to consider is the fact that you are already avoiding hits, and you are now going to avoid +4% (additively) more. The formula is rather simple:

Reduction = 1 - (1 - %Avoidance_SS) / (1 - %Avoidance_No_SS)

Those values are pretty easy to pull off your armory sheet, and that comes out to about ~5.6% before raid buffs (ignoring expertise). Again, in simpler terms, this means that the total damage you take (note the slightly different wording) will decrease by about 5.6% if you use SS.

That's actually not entirely accurate, as there's some interact with mastery (gains and losses), but it's a nice ballpark.

As you get more gear, you also get more avoidance. As you increase your avoidance, SS becomes much stronger (because it's a flat +4%).

Anyway, if you want to more or less "directly" compare those, just divide the %'s. 5.6% / 2.6% = 2.2, so SS is going to be somewhere around 2x as good as SSG for you.
The key to it is to get out of the stigma that your health pool is how you are a tank. When doing 5 mans most will remark if their tanks do not have a lot of health. So when gearing the tanks may gem full stam, use stam trinkets and for dk throw on gargoyle. But it's not necessary. Generally your health should be high enough for the damage even from caster mobs if you use your abilities correctly. That is why Sword Shattering is better. 4% avoidance that is separate of our diminishing returns is extremely good. The more parry rating you get the more of the parry rating it takes to get a % of parry. Sword Shattering is not part of the diminishing return. So when you only have 10% parry in your gear it grants 4% extra. If you had 18% parry rating in your gear it would still grant 4%. This is what was implied by the comment that the more avoidance you have the more you get out of Sword Shattering by it's design.

TLDR, Mastery is your bread and butter and when used and prioritized correctly will not require a giant health pool and that is why Sword Shattering's avoidance is the best. If there was ever a reason to use Stoneskin Gargoyle it would have to be a very specific fight where the mob doesn't melee at all and thus we can't even parry the attacks.