Well, to play devil's advocate.. providing a mathematical model that can accurately capture the scope of tanking, and the ability to configure that model for the desired scenario, it really is directly possible to mathematically rank the value of each stat for both DPS and tanking. For example, here is how the Chest enchants rank in a Time-to-Live calculator according to my bear form stats against Azgalor (measured in extra seconds the enchant allows you to live):
0.1787 Enchant Chest - Defense +15 Def
0.1785 Enchant Chest - Exceptional Stats +6 Stam, +6 Agi
0.0998 Heavy Knothide Armor Kit +10 Stam
0.0881 Enchant Chest - Exceptional Health +150 Health
0.0877 Enchant Chest - Major Resilience +15 Res
While it's certainly not the only method for ranking tanking gear, we're theoretically talking about a very complex mathematical equation. There is a correct answer, always. The equation just has hundreds of variables.
