Guardians have their 1-point paragon trait (Ursoc's Bonb) reduced to 6% armor bonus from 10% on PTR. Guardians have "Fortitude of the cenarion circle 1 point new trait giving 12% armor rather than 20% as other tanks have. Let's compare that to a blood DK/warrior/pally- they get 10% armor from their 1-point trait and 20% more from the other one
Bears- 18% armor bonus
Plate tanks- 30% armor bonus.
That's quite substantial. I guess this is Blizzard's intention of brining bears more in line with other tanks.