Rebuttal does not necessarily solve problem because appraisal is

10% variance is normal. You and your loan agent have to have extensive knowledge about the comps to challenge the appraiser.(You can bring $$ in to lower your mortgage balance if you still want your refi to go thru.)

In terms of reducing property tax, you have to read your property tax statement to see what's the county appraised value. If the county appraised value is same or lower than what's on your appraisal report, you won't get anywhere...