Exactly this. A good bear tank not only has an arsenal of trinkets at his disposal (no use trying to dodge magic dmg) but also the possibility to reforge, re-equip some gear where needed. none of this reflects on armory nor how much the bear is in tune with the damage he takes from one fight onto the other and which steps can be taken to reduce this.
the age old discussion of stamina or agility is also an important factor as time and time again it is proven that a sta inflated bear altho on paper has less mitigation and looks like a worse tank than the agility stacked one, with certain fight mechanics, and realising what kind of healing capabilities your raid has this effective health will/might actually make the 'worse' bear survive.
so knowing that all of this and much more needs to be taken into consideration on a fight per fight basis i rate all bears 10 for effort
but truely judging them is impossible without knowing all the parameters.