Enchant Gloves - Major Strength (+15 str) is ranked at 0, things like Heavy Borean Armor Kit (+18 stam) and Enchant Gloves - Expertise (+15 expe) are ranked at 15. Even things that add just attack power are ranked higher. As great as +35 or +45 AP are, for a prot tank, str is important because it not only adds attack power, but adds block value. Now this logic would be understandable except for one thing, Enchant Weapon - Potency (+20 str) is rank 15 for swords. What is the logic behind having certain str chants worth anything, and others not. Also, making AP more valuable than str isn't 100% true for all tanks. Maybe DK's who don't block, but anything with a shield values str.
If you want an example of this view Hannor on US - Azuremyst