Robe of the Elder Scribes
Robe of the Elder Scribes is an epic cloth chest armor for DPS casters.
The temporary damage increasing effect has a 20% proc rate. In game testing over raid boss fights has shown an hidden internal cooldown of 50 seconds resulting in a proc rate equivalent to 1 PPM. With a PPM of 1, the proc can be compared to +22 spell damage all the time.