Why all the hate?
18stam = 190HP with talents, 209 when adding kings, yet when rating enchants...
heavy borean kit: 5points
150HP to chest enchant: 10 points
200HP to chest enchant 12 points
Yes, 15 expertise is awesome threat and will reduce damage slightly with fewer parry hasted swings (we're talking less than 1% reduction here) but I'd call it more equal to 18stam instead of 3 times more valuable at 15 points. Also the 240 armor kit has been worked out to be less EH than 18stamina yet gets 2 points more than the kit at 7 never mind the collection of glove enchants listed that have nothing to do with survival, only your threat and DPS which somehow rate higher on the scale.
EH is the first thing to measure when deciding whether a tank belongs in a particular instance or not. Threat (and DPS) comes after that, it has to.... a dead tank holds no threat.