This is helm enchant is considered to be better for most tanking situations than the Glyph of Defender. The reason people still take Glyph of Defender is it's ease to obtain.
Just throwing it out there that someone with it shouldn't be told a recommended upgrade is the Glyph of the Defended as it does depend on the situation.
Stam and threat vs avoidance.
http://elitistjerks.com/f31/t18771-prot ... ior_guide/