I don't think I editted anything. But here is the WWS, maybe it'll help?
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I was under the impression that Guardian Spirit didn't work on Bears (there are many many posts regarding this on the WoWForums). Basically, I think you guys just got lucky.

I've had Guardian Spirit save me in bear form. Unless its a bug that doesn't always happen...

I am clearly out of touch with how resists work now, it seems that it no longer follows a 0-25-50-75-100 percentage scale.

I am also quite sure that guardian spirit works sometimes. I estimate i used spirit cca 10 times so far and i recall 1 failure but i didnt know about the bug so i just dismissed it (i survived).

My experience with this fight has been very similar to the others. The first few times we did the fight we actually did it without any kind of save the bear rotation, which I would not recommend. One of our priests has recently switched to Disc. and between Spirit, when it decides to work, and PS that is usually enough to get us through the TT phase of the fight.

For those of you that are Leatherworkers do you feel that the +90 Stam or the +60 Fire Resist to bracers is more beneficial in this fight? I personally am using the FR to help mitigate a little more of the Breath and random cyclone damage. I haven't found the loss in health to be an issue.

Nightcrowler, kind of in summary of what the others have said. The fight is really only going to be bad for the Sarth tank and his/her healers during the Twilight Torment phase. As soon as Vesperon opens his portal I stop attacking/using anything that will activate my GCD. During this phase you will die if you take a full breath attack from him. Several ways to mitigate the breath are:
Pain Suppression from a Discipline Priest.
Hand of Sacrifice from a Paladin.
Barkskin/SI from yourself.
Guardian Spirit from a Holy Priest. (Although like the others I have seen this not work 100% in the past, haven't noticed any issues on Sarth 3 though.)
In addition to mitigating the breath with a cooldown, you will want to try and avoid/dance the TT debuff. When Sarth begins casting his breath, you will need to find a spot that works for you based on latency and close enough to the end of the cast, use an instant attack like Mangle or swipe. This will trigger the TT debuff and you will take 2-3k damage, the debuff drops for a very brief period of time (between 1 and 2 seconds).
Expect to see between 2 and 4 breaths during the phase with TT and Shadron both alive. Once Shadron is down it is pretty much game over. You no longer need to worry about a save the bear rotation.

We 1shot sarth+2 last week and are planning to start work on sarth +3 this week. I have a set that gets me ~55k buffed (polar pieces + PVP pieces).

My guild is also in a nice situation in that we have 1 pretty well geared tank of each class, meaning that along with me, we also have a well geared DK tank. My main question is wether it would be better to have me tank sarth, or the DK. It prettymuch seems to come down to my larger health buffer Vs his better on use mitigation abilities such as boneshield, icebound fort and anti-magic shell.

Have any of you experiened both classes tanking and have any input as to which seems more effective given that both are available?

Sorry, I should mention that I am specifically talking about 25man. Last week (2 drakes) we had myself on Sarth, a pali on the blazes/welps and a warrior on the drakes with the DK sitting out. In tank chat, both the pali and DK seemed to think that the DK would make a better tank for when we do it with 3 drakes up.

We use 4 tanks usually, 2 on the adds. How many healers are you using? Our breakthrough came when we dropped from 7 to 6 to 5 healers for it. The extra DPS lets you down Tenebron before Shadron and unless you're unlucky on walls, Shadron before Vesperon. This pretty much trivialises the fight as you don't get the cross over of Power of Shadron - Spell - World of Warcraft and Twilight Torment - Spell - World of Warcraft together making it so much easier. After that you just have to have someone that can take the blows of Sartharion once all the drakes are down, its a non-trivial increase in damage taken, its why I don't advocate using the Polar set for 25 man. Either that or you can have the drake Warrior tank in his normal tanking set taunt it off you at that point.

As for Guardian Spirit I've never had any issues with it and have seen it several times save me from a killing blow and top me up (whilst disappearing as its consumed).

This was my thinking also. My main question still stands - assuming we do have a number of critical breaths do deal with, what is better from a healing/surviving perspective while we are learning the fight - a feral with a high HP buffer with barkskin/SI for 1 breath, or a DK with multiple CDs available to him. Assuming both will also have outside cooldowns being used on them. Do you feel the difference between the 2 tanks trivial or that the benefits of 1 outweighs the other.

Much like a how feral makes the best OT on patch, or how a warrior/pali's block mechanic makes them better at taking a lot of small hits. All tanks are obviously viable, some just more-so in specific instances.

DKs are pretty awesome at tanking the whelps/adds to be honest. Taunt, Deathgrip, static and "mobile" aoe damage skills. Given the choice I'd have them doing that every time.

Sounds like someone wasn't happy about sitting to me. The DK or the Druid will be effective given that both players are equally skilled.

From what I've heard/seen on 3 drake a DK's cool downs is what makes or breaks it. If he has enough to last while you guys kill shadron, then he's fine but once all 3 adds are down you better have a mitigation geared tank taunt because the DK is going to spike hard with 75% increased physical from Sartharion.

Again that is from what I've seen, it could be that I've just seen some terrible DKs and that they do fine tanking him after all the drakes are down.

BLing on the first or the second drake doesn't really matter unless you can reliably get the first drake down before the second drake without a bloodlust. As long as they overlap at all, they essentially share one health pool (since you won't be killing the second one before the first one).

If you can't see the TT debuff for whatever reason, you must set up a cooldown rotation for the breaths. Otherwise you will die. The other option is to stop attacking entirely when Vesperon hits (turn off autoattacks too) and make sure to only attack when a breath is coming. Even then, I'd want to see the debuff get removed.

I had the same issue seeing the Torment debuff - I set up a custom Grid Debuff Aura as a 99 priority center icon, and it appeared consistently (it looked like the Vampiric Embrace icon). However, I can't get BuffBars to find it, nor does my custom SCT Alert show it. I have a hunch it has something to do with the source of the debuff being in the twilight realm, but that doesn't explain why Grid shows it.

I guess that's because Grid only updates Debuffs in an intervall greater than the time TT actually is inactive.
For Sarthaion+3, I'm using a seperate group of Elkano's BuffBars with really big bars solely filtering my own debuffs, works fine.

Best and least-fussy way I've found to deal with debuffs on yourself is to install Buffalo. Move the debuff frame to above your character's head and enlarge by a little.
This way you can always see debuffs on your own character without having to look for them elsewhere in the UI. Also it's very fast to respond and I find it 100% reliable for attacking to remove TT before each Flame Breath hits.

Strange. Elkano's Buff Bars shows Torment just fine... If you have problems seeing the debuff, are you using any buff/debuff mods, or the default interface?

I don't think they stack, it just means that a larger buff won't remove the scroll buff. It's not particularly relevant for the stamina scrolls, since the stamina buffs are all longer than 30 min. The problem was with agi and str scrolls being overwritten by totems or Horn of Winter. The wording of the patch doesn't imply that they'll stack, just that they can coexist.

Indeed, I probably assumed too much. It should probably indeed be seen as the MotW and Shadow prot buffs. Though MotW will give shadow protection (as stated in the tooltip of the buff) this is not used because it is overwritten by Shadow protection.

It's supposedly fixed in 3.0.8, but it's been noted here:
MMO-Champion BlueTracker - GC: Direct Priest Questions ONLY

It looks like Ghostcrawler here pretty much acknowledges that it wasn't working.

There are also multiple threads on this here:

World of Warcraft - English (NA) Forums -> [BUG] Guardian Spirit and Bear Tanks
World of Warcraft (en) Forums -> [HUGE BUG] Guardian Spirit

Anyways, probably not worth further discussing, since its "supposedly" fixed, but it didn't work on Sartharion breaths for me.

I'm pretty sure they work on a 10% scale now, which provides more even resists (although it's still random). I unfortunately didn't find many good resources researching this, and I suppose that most people have no motivation to do so because there isn't a fight in game that really stresses resists at all.

All the old resources regarding resists, including wowwiki, are all outdated now.

As a minor note here, Torment shucking is out the window, so you're going to need either fantastic DPS on Shadron or some cooldown help to survive the hard crossover. Whether it was a wise way to go is moot, as they've apparently changed it from dropping and reapplying to just having an ICD on the damage you take from it.

I'm trying the method of stacking FR gear. So far it's looking promising; I'm taking much less damage than I was before. I am hoping that barkskin->instincts->barkskin should make it through three breaths, and then the 4th I can hopefully be or Shadron will be dead. I have, IIRC, 280 FR with raid buffs, flask and gear.

Assuming the server lag abates, we're hoping to try this tonight. I'll let you know how it works.

ETA: you can, by the way, get rid of the debuff by hitting one of the blazes apparently. Faerie fire works for this as well. You may want to taunt and tank a pet blaze during the easier parts of the fight and use that to get rid of the debuff.

That's gonna hurt a bit.

Although 25-man will likely have enough people to cover you for cooldown rotations, 10-man is going to be extremely harder now.