I notice it too, but it's obvious why when you consider the tank meta shuns tankiness. From what I've read (I haven't even unlocked any tank classes yet), tanks are told to shed any signs of vit from their accessories and run pure Slaying (DPS) gear. They also like to tank in DPS stance rather than tank stance. The DPS checks in savage Alexander raiding make it a huge boon for tanks to run like this, and because other content is easier, it's trickled down in to the leveling dungeons and such. Ultimately, if a tank doesn't have the good sense switch to tank stance/pull less, just be on your toes and keep em healed.