Indeed, class considerations are pretty important here. Warriors, with their low Stamina multiplier and low Armor values can really get a lot out of Bonus Armor items. They are very powerful for us compared to alternatives.
However, Stamina is really, really good for Bears. So, not too surprised that the value can go back and forth based on that.
Martie makes a really good point and definitely is a large reason Armor is a nice stat, especially at large values that give solid EH as well.