I guess recalculating my FR set is in order then.

Fire Resistance Aura, Lesser Flask of Resistance, Arcanum of Fire Resist, Enchant Cloak - Superior Fire Resistance, Fur Lining - Fire Resist. Results in 285, 49 more is needed from other gear. For me this will come from Shoulders with 41 FR and a Flame Kit.

This is actually comforting for me, the sacrifices I was making to get 415 AND 50k hp were uncomfortable, and I still died to 30% resists, not being topped off, and ending up taking too much physical damage from having lower armor/avoidance.

As an aside, the [Effulgent Skyflare Diamond] still isn't working in the manner listed by others for my FR.

Last Night was my first kill in 10 man as well, using the 334 FR gear I listed previously, ended up going with 3 tanks (Warrior on Drakes, DK on Whelps/Blazes). Holy Paladin on me, Resto Shaman on the other tanks, Resto Druid for raid. I ended up taking 5 breaths during the gib phase (we don't go into portals until all Drakes are dead, though we likely could, SI carried me through 2 Breaths (with Frenzied Regen to make sure I was topped off), Barkskin was used on first and fifth, and a fire pot for the 3rd. I actually carry a stack of Frozen Runes from old Naxx in case of a 6th bad breath. Honestly I see no reason to not to use the cooldowns available to you ever time, FR pots are cheap and cooldowns are free.

Neone, one thing to remember is that you're well within the range for getting 20% Breaths, so the max breath going to be 51973, which is actually above your full health even with Survival Instincts (with grace take off another 1.5k, which is still very close) I don't know why as a JC/LW you aren't going for the minimum to guarantee a 30% resist.

Nightcrowler, considering blizzard doesn't use a multiple of 3 for Spell Miss %, I'm willing to accept an arbitrary 25% difference for Bosses Spell Resists. Another possibility is that we're still looking at Piecewise Linear functions, except with 10 of them, this would explain Minimum Resists and the "curve" in resists people see.

Ya that chart might be a little confusing, listing average resist when we've been talking about minimum possible resist.

I'd like to mention I feel quite guilty when people mention these numbers I quote as resistances they shoot for... I just hope you're all keeping in mind this is still very tentative data, and a work in progress, so don't be too too mad if you still get one-shot ^^. Keeping logs while you wear various amounts of FR can be very helpful in nailing these numbers down for good soon, so we don't have to keep saying "tentatively...."

I was tanking sartharion 3D both 25 and 10 few days ago and would like to share my experience.

285 resistance (flask,aura + enchants on cloak head and wrists), full polar set (+ring), JC trinkets. I had ~39.5k hp post Vesperon aura and ~41k+ with warlock pet banished near my tanking position (we had only 1 warrior for shouts and he was busy with dragons tanking).

Apparently I did have some 20% resistances, but it never caused a problem. on 25man the max fire breath damage during the "hard phase" was around 46k, which is easily countered by barkskin, SI, HoS from pala (need to call upon), second barkskin. potion + nightmare seed would make another one, but at this time Shadron is normally dead already.
At this point you might need a bit more healing, cause Sartharion is getting his melee damage boosted, just make sure to warn the raid about it.
After killing Shadron, we are going to Twilight realm and kill both acolytes. If you are still alive at this point - the fight is more or less done.

for 10man we used 3 tanks/3 healers setup.
dps was ench. shaman, hunter, ret paladin, shadow priest.
The target was set to kill Tenebron fast, then clear the area from all adds. After that the focus was on survivalability rather than on making damage, Dpsers were told to stop attacking if they are at 50% HP.
I'd say at this point (Shadron+Vesperon alive), the dragon tank survivalability was more problematic than mine one. We used a warrior on that, so he was saving his shield wall and last stand for this phase, still it's not enough for the full duration. We had quite a few cases when he was gibbed by double breath+some melee and Twilight debuff proc.
As for me (Sarth tank), maximum breath I've taken was sub 38k, with my max HP 39.5k. I was trying to save my cooldowns for "dangerous" cases. For example if there is no lava wall incoming, if I'm topped, healers are standing still and just healing, I didnt use anything. Otherwise, barkskin, potion, SI or frenzied regeneration.
With such rotation, I could tank him infinitely long. Next time I'll bring lvl70 fire res gloves, hopefully that will remove 20% resistances and tanking will be even more safe.
I had holy pal on me 100% time and resto druid hots during shadron+vesperon phase.

The general impression of feral fire res tanking: it's easy and reliable. We had a DK tank on it before, and he was dying quite a lot (not sure, maybe he was not doing right things thou). 75% of gear you will need for it is obtainable by crafts or from pvp - I used pvp hateful pvp gloves for badges and hateful wrists (normally I play resto). Plus a few offspec rolled pieces and the full set is ready.