This happened to me (and certainly not for the first time).
I’m building a Penetrating Shot build for my level 43 rogue, and I wanted to temper my 2H and two 1H weapons with “Chance for Penetrating Shot Projectiles to cast twice.” The result?
None of the three weapons ended with what I wanted. NONE. The temper I was looking for NEVER even appeared once. So my 2H now has a temper for Twisting Blades, my 1H’s have a temper for Barrage, neither skill of which is in my build.
This tempering system is the only feature that has vexed me immensely in Season 4.