First off, it's 156 Defense Rating, not 154. I think this number has been misquoted at least 10 times in this thread, so I'll bold this for everyone.

156 defense rating / 2.4 rating per defense = 65 defense. 65/25 = 2.6% Crit Reduction

And that's not how Itemization works in WoW, 102 X + 52 Y =/= 154 Z.

All stats (except Sta) and ratings cost 230 'points' each.

Defense: (156*230)^(3/2) = 6,796,395
Resilience: (102*230)^(3/2) = 3,593,287
Difference = 3,203,107
3,203,107^(2/3)=21729/230 = 94.5

So for the cost of 156 Defense, you can get 102 Resilience and 94 Agility which is ~6.38% Dodge, 3.76% Crit, and 188 armor, compared to the 5.2% Avoidance from Defense.

Of course, it's going to be spread out between multiple items, so it's actually looking like:
Gilded Thorium Cloak: 24 Rating = 10 Defense = .4% Reduction and .8% Avoidance
Instead of Defense it could have had 16 Resilience (16/39.4 = .4%)
and
(24^1.5-16^1.5)^(2/3) = 14 Agility = .95% Dodge

So even with rounding errors in favor of the Defense (rounded Resilience up and Agility down) it still loses.

This is what I touched on in the Feral Druid Pants Dilemma thread. Thankfully, I'm finding that Agility is so good (better than Strength) that a Skulker's Greaves (the new kind) full of +8 Agi gems is straight up better than T5 pants for DPS, which leaves the option of using T4/T5/HCL for tanking depending on what is needed and what I have.

A lot of people don't realize exactly how good Agility is for DPS when calculating this stuff. According to Emmerald's spreadsheet (updated to include my unbuffed hit/crit/AP as well as factoring in Kings) for me, Agility is worth about 2.75x what 1 AP is, and Strength is worth 2.64. For comparison's sake, Crit Rating is worth 1.75x AP. It's a disgusting divide, but it means that anything with "of the Tiger" style stats or anything with sockets so I can stack Agility is FAR better than anything else for DPS.

Hullahop: It's 'not bad' if you don't have any better, but as far as I'm concerned, ring and trinket slots are for Druids to abuse the armor multiplier, with the exceptions being if you're already comfortable with your AC and something has a ton of Stamina on it, like Argussian for example.

You'd probably be best off trying to grab Lt. Drake's AC ring... that's not bad for a starter.

For me, Delicate Eternium and Shapeshifters Signet are both "An Enh Shaman/Rogue could probably tank this" rings for me still. Tanking one of the first adds on Magtheridon, Hydross, Maulgar's Priest, etc. presents excellent opportunity for Agi stacking as a means of tanking that will be followed by dps later.

And Warriors everywhere cried out in pain ... Yet another tanking reward that's useless for them.

I honestly would have rather the Magtheridon head reward be for warriors for once (I could take the DPS ring guilt free!) and give druids a drop (or Kael/Vash head reward) for tanking to replace the many Early Kara or lower items we'll be using in Black Temple (Neck, Cloak, Wrist, Gloves, Waist, Boots, Idol, Trinket, Weapon ...)

I believe Boevis' answer was one big yes.

The Maggy head ring is slightly behind the exalted Violet Signet.

Looking back at Exewut's screenshot in this post: Bear tank item comparisons I'm not sure in the long run Magtheridon's ring is the best min/max item. But then again, when I see Magtheridons's head drop it will definately be a large enough armor upgrade for me.

Hmm, anyone else having difficulty deciding which meta to put in t4 post patch?

Problem is, it's the best tanking headpiece available at that level of progression by a looong way, but also the best for dps. Gladiators and that new badge reward helm pale in comparison. I'm caught between keeping the powerful earthstorm (18stam 5% stun resist) I have at the moment or switching to that new one, relentless earthstorm (12agi 3% crit damage) which incidentally has had it's requirements reduced to 2 of each color if I recall correctly.

I suppose the other option is to get 2 x t4 helms..

Personally, I was preoccupied with trying desperately to staunch the bleeding from my eyes.

A more optimistic take on the stats would be that the Strength on that staff allows you to drop some Strength from elsewhere in your gear in favor of more Agility-heavy item(s) perhaps. I do wonder how Blizzard will approach our itemization moving forward though, as I came to the same conclusion as Kazanir re: STR vs AGI for kitty dps while playing with Emmerald's numbers a while back. If they want to make druid leather distinct from rogue leather and do so in a way that's not as ham-handed as putting class-specific modifiers and bonuses on lots of items, then it sure seems like they need to revisit the relative value of STR and AGI for these classes. For purposes of keeping itemization streamlined however, having significant overlap between [Good for Druids] and [Good for Rogues] isn't a bad thing at all.

Regarding the lack of tanking stats, I've found it's generally good policy to take the advice of many regular posters here and wait until we have a more complete picture of how Blizzard has populated a given tier's loot tables before raising a big stink about itemization holes. In other words, it's possible that there's an evolutionary Earthwarden/Wildfury Greatstaff out there that hasn't (a) dropped on PTR yet or (b) been implemented yet.

I don't even pay attention to Strength on my tanking gear. If it's there, yippee, but it's nowhere near a high priority, hence I don't have a lot of pieces I have sitting around where I could find myself replacing them with an agility item. I know if it were Agility, it would be obscenely amazing, but a bear can dream. Not like I'd ever see that anyway, in any case.

Every needs to make sure they understand Boevis's math. It is not as clear cut as saying that Resillience and Agility is better than Defense.

Since he uses the (^3/2) to denote a stat split on an item, you have to have an item that actually has both Agility and Resilience to take advantage of that math. But really how many items have agility and resilience? Until you have an item created as such, this math is useless.

Taken as a pure stat, Defense is still better point for point.

Thus when making decision on one-off stat increases (as in the case of gems or enchants), Defense is still a better stat.
Also note, multi-colored gems split points on a linear scale, not on the logarithm scale.