Against 10 mobs, assume that you're maul/swiping. You'll land on average 2 hits every 2 seconds from maul, plus 10 hits times 1.5 seconds with swipe. Assume 33% crit, and you have independent 5/9 blocks every 2 seconds and a 96% block every 1.5 seconds. Enemy swing timers of 1.5 seconds, and you get 10-15% total damage mitigated (assuming the swings are for less than your total attack). And that's at 0 avoidance-- at 50% avoidance you're eliminating 20-30% of damage.

The full 66% armor buff we get from SOTF (additive to the rest) increases our total armor by .66/5 = 13%. That 13% armor would take 30k armor to 34k. 30k armor does 64% reduction, 34k does 67% reduction. 3/37 is approximately 8% total damage reduction.

So, from 8% reduction to 20%-30% sounds like a net gain in AOE tanking, to me, even if they eliminate SotF armor entirely.

I was wondering if anyone else would notice this, I certainly hope the savage defense shield does not reduce rage from incoming attacks. And more generally, why not let both druids and warriors get full rage from all absorb effects? (power word: shield, etc).

Yes, I too mourn spirit's fall. I wonder how, mathematically, they will perform this nerf. I expect they'll probably slap a scalar on the spirit term in the regen equation, something like:

regen = .005575*5*.8*Spirit*(Intellect)^.5)

I don't really see how else they would do it. Since they will keep the while casting regen the same while buffing Intensity, we can do this:

I(.005575*5*N*Spirit*(Intellect)^.5)=.3(.005575*5*Spirit*(Intellect)^.5)

Most of the equation will cancel, yielding:

I*N=.3

N=.3/I

So the nurf scalar number will equal .3 (the old Intensity) divided by whatever % they choose for the new Intensity. Of course, this is all speculation. I'll have to check it out in the PTR to see how this will go. I don't expect spirit's MRV to drop below the .2's, though.

EDIT:

However, I am thoroughly excited that they're considering changing clearcasting procs to a burst of mana. That would actually make the darn Omen of Clarity talent modelable.

Another thing that came to mind with the change to the OoC regenaration is [Darkmoon Card: Blue Dragon] will become a lot less effective. While not really required in current content, I was hoping to pair it up with another regen trinket in preparation for Ulduar in case there will be longer or more healing intensive encounters.

With regard to Savage Defense, in the case of hard hitting bosses like Sarth3D & Patch, the ~1.5k shield is pretty small compared to the size of the hits coming in. In addition to this, our crit rates aren't particularly high and on the big hits you take, you will be taking more damage than currently due to the armor reduction.

It seems that overall we will take a bit less damage (helps healer mana a small amount) but the risk of us dieing in an encounter seems to be higher than we currently have. I hope they look at this talent closely as to me it feels like we may be better off now than with what they are currently suggesting.

That is one good thing about this change, people can finally shut up about that damned stupid card because it's bad and needed to die last expansion.

Are we ever in danger of dying to an attack or flurry of attacks that are armor mitigated though? Bear tanks get to levels of health where sarth can't kill them with a triple-drake breath: it would seem that the risk of being insta-gibbed is, at present, effectively nil.

So the issue is that worst-case mitigation goes down, while average mitigation would appear to improve (unless the internal-cooldown gremlin screws up yet another balanced mechanic...). That just means that the stamina soft-cap will go up.

First, they seem to be struggling with rage generation much more than we do.

Second, by tying it to crit, Primal Fury ensures that any time the shield goes up you get 5 rage.

I did some math on what the armor values would need to be . It's a bit rough, but the long and short of it is that if the armor reduction from SotF is on the order of half the bonus, it will be a nerf to bear mitigation against Patchwerk-level bosses (but not a great one). Against more typical bosses it will be an overall wash. Against multiple mobs it will be a very large buff unless the armor bonus from survival of the fittest is actually outright removed.

Wow, when I read these proposed Savage Defense changes I nearly spat my drink out! As it is exactly the sort of thing that was discussed here pre-wotlk and I actually suggested something near identical:

http://elitistjerks.com/971867-post3674.html

Similarly as was discussed back than, it would need to have stackable charges to be truly worthwhile. Otherwise it could be much harder for us to tank faster hitting bosses, especially those with hard hitting specials. Something like Halaazi from ZA with very fast auto-attacks but a powerful Sabre Lash.

People say, that SD coming along with lower armor modifiers on SotF will be an overall nerf to bear aoe tanking. Let's take a look at this (more napkin math inc):

The difference in dmg reduction is roughly 8% between bears (70%) and warriors or paladins (62%) when it comes to armor mitigation (not sure about dks at the moment). The mob taken from the ThinkTank example deals 10k with a swing timer of 1.5sec. I can't think of an example, where actually 10 mobs need to be tanked at once (maybe utgarde pinnacle or maexxna?), so let's just take this one. We leave out any avoidance, so keep in mind, that 10 hits is already the worst case when tanking 10 mobs at once.

According to the ThinkTank this can be expressed as 1 mob hitting every .15sec. for 10k. With a shield proc occuring every 1.2sec every 8th hit is mitigated by SD's shield. With current numbers, the shield will absorb 1250 dmg. So the mitigation we gain from SD is 1250dmg/1.2sec.
How much do we lose from the loss of armor mitigation?
Blizzard thinks about bringing bear armor in line with the armor other tanks have. So, regardless of the actual numbers, this would require a loss of about 8% mitigation. So lets see what happens, if the lower SotF modifiers result in a 8% mitigation loss (note that at this point I ignore the fact, that this might not even be possible, even if SotF would not give any bonus armor. We will see later on).
Every hit would be mitigated by an additional 8% which is 800 dmg per hit. In 1.2sec. we get 8 hits, so we gain 6400dmg/1.2sec. This is in fact better than SD, but it is also absolutely unrealistic, because we ignored avoidance. Considering avoidance and misses, the benefit of 8% more mitigation from armor is reduced to approximately 3500dmg/1.2sec effective dmg reduction.
So far, armor is still far ahead of SD and this is why people keep saying, that SD is bad for aoe tanking.

What a nerf of SotF is needed to achieve a loss of 8% armor mitigation?
Again, using the ThinkTank numbers 29866 armor results in 64% mitigation. 56% mitigation is reached having 21k armor. This means Blizzard had to reduce the SotF bonus to something like 5/10/15 which is highly unrealistic since this would bring us way below other tanks. It is realistic to drop us to about 25k (60%) which means something like 13/27/40. This is in fact only 4% loss in armor mitigation so the above aoe tanking example would cut the effective dmg reduction to 1/2. 4-5 hits during a 1.2sec. period hitting for 400 less dmg means 1600-2000dmg/1.2sec.

In conclusion, bringing us exactly in line with other tanks armor wise, SD will be a slight nerf when tanking 10(!) mobs at once. We reach a balanced state at roughly 3 hits taken per 1.2sec. (1200 more dmg taken because of 4% less armor mitigation and 1250dmg less dmg taken due to SD's absorb). This is the case while tanking 6 mobs at once (2.88 hits per 1.2sec). So, whenever we tank a total number of 6 mobs or less at once we actually benefit from Savage Defense, even if the bonus of SotF is reduced to bring us exactly in line with warriors and paladins. In other words, unless Blizzard reduces the SotF bonus below 40% at 3/3, SD will be a buff everytime we tank 6 or less mobs at once.

Note: Actually I had this all done earlier, but I didn't have the time to post the results. Then, kalbear came up with his ThinkTank entry and so I decided to change my calculations in a way to reflect his numbers and to prevent reinventing the wheel.