As an Enchanter with the maxxed "Quick Buff" AA, I have absolutely ZERO use for any Focus that gives beneficial spell haste; I'm maxxed out at +50% just from my innate AA.
I wish they'd take a page from the coder who re-did the Wristbands, and make different versions of the armor with different Foci, so everyone could customize w/o wasting a precious armor slot with a Focus you cannot use.