You're right, I forgot to link Emmerald's, although from what I understand his gear list was constructed during Wrath's beta and hasn't been updated since (I'll grant it's a huge list to update, but a lot changed in 3.0.8).

The Polar set is indeed a fast and cheap way to get a lot of stamina, and that's the reason why it tends to get ranked so highly on static gear lists. Even the creators of said lists will tell you that stamina is weighted fairly heavily in how they rank gear. And there's really nothing wrong with that; stamina is our best-scaling stat. But because the Polar set just has so damn much of it, it overrides the weightings of other valuable stats.

And while stamina's great -- more won't hurt you -- you're giving up a ton of expertise, agility, dodge, +hit, and +crit that you'd be getting using different pieces. Expertise and agility are particularly important there -- you can make a fairly good case that for the amount that the average raid boss will be hitting you for, the stam you get off the Polar set will in no way make up for the damage you'd be avoiding with more dodge or enough expertise to begin pushing boss parries off their avoidance table.

So while the Polar set isn't bad and it's decent gear to start tanking in at 80 when you do need some health, it's not gear I'd try to stay in simply for the sake of that health. A starter bear tank with Polar and greens/blues rocking 35K health looks impressive, but they're hell to keep healed.

With all that said -- the Polar set gemmed and enchanted for stamina makes marvelous tanking gear for Sarth with 3 drakes up and that's what I use for main-tanking that fight to push my health to about 53K without Jewelcrafting or Leatherworking. But once the drakes are down and Sarth actually starts doing decent melee damage, we have one of our prot warriors taunt off me -- I just take too much damage in that gear to make it worth it for me to finish tanking him. It's great for soaking Sarth's big breath attacks. It's lousy for mitigating or avoiding damage otherwise.