According to this question and the answer Ashkenazi shat”z?
Someone who pronounces an ע and an א the same can be shat”z, as long as everyone in the shul does so too. What if a couple of people pronounce them differently, but most pronounce the letters the same? Or what if half the shul pronounces the letters the same, and half differently? Would the Halacha be different, or would we go according to the rov?