This isn't just fascinating in and of itself, but in what it reveals about what is possible for gear going forward. If bonus armor items can have strength and agility, then it's feasible that all Warlords weapons could have strength, agility and intellect and only display the one that's useful for the class and spec using it - a 1h mace could have strength for a DK, agility for a shaman, and intellect for a priest. It's the flexibility of the potential design that's the most interesting, and obvious, departure from the original game.
There are many things to consider about how gear is changing. In a very real way, it's almost as if the removal of reforging has combined with this idea of situational stats, and is now going even further (bonus armor, a secondary stat, will now grey out for non tanks) - we're as close as we've ever been to gear that is useful to every single class and spec. What's left are a few things that we know won't be changing - armor type, for example, seems to be a hard and fast unyielding barrier. Cloth, leather, mail and plate will remain as they are, and your priest won't be wearing gear that scales up and down to match the class. Quite frankly, if that were going to be the case, there would be no reason to have armor types at all. But we do already see a certain kind of gear that does this - heirlooms that go from cloth to leather, or leather to mail, or even mail to plate do this already, in one direction.
What's we don't know yet is, could this kind of design be extended? Random proc items like Gurthalak, for example, how will these be handled? Well, it's possible that they'll simply be rare or nonexistent. But there are some very tempting alternate ideas. You could easily design a weapon with a proc that greys out when used by the wrong spec, or even multiple procs, only one of which works for a certain role. Imagine a 1h sword with a self healing proc for tanks, a damage proc for melee DPS, a different proc for raged DPS, and yet another proc for healers? It might not happen... but it could.
Especially with tanks using bonus armor as both a survival and DPS stat (all tanking classes will get the Bladed Armor ability, adding attack power from bonus armor) you start to see ways in which specific items could be designed and engineered to provide synergy with class or role abilities in unusual ways. Bonus armor gear will provide a solid amount for the tank seeking it, yet that bonus armor is effectively useless for a non-tank. Yet the item can have other stats on it, which will grey out when worn by a tank, if the designers so wished. There's an amount of restraint needed, or the game could quickly become 'everyone wants every item that drops if they can possibly equip it' - and it's that line that's something we'll all be watching, because gear is now much more a question of simply plugging it in and going. Without as many enchants and gems to worry about and no reforging, the gear having the ability to customize itself to you, instead of you customizing it becomes very important.
We've heard quite a bit about how these changes to gear will affect us, of course. Some classes will see specific changes because, at present, they're very dependent on specific secondary stats. This means that there won't be as much pressure (hopefully) to stack a specific secondary stat, like crit. And this means that we don't need to worry about getting to the point where certain classes almost wish they could grey out haste or what have you. It's fairly certain, however, that gear design in Warlords will be more restrained than it could be - the development of how the bonus armor stat is going to work certainly suggests it could get a lot crazier.