Comparable-property assessments can provide evidence when evaluating uniformity. A meaningful difference between your property and genuinely comparable properties may deserve closer review, but the comparison must account for relevant property differences and the rules used by the applicable assessing or appeal authority.
Uniformity and overvaluation are related but distinct concepts. Market-value evidence may be relevant to an overvaluation argument, while assessment comparisons can be relevant to a uniformity argument. Which evidence is accepted and how it is evaluated depends on the jurisdiction and forum.
The difficult part is identifying useful comparables. Relevant characteristics may include property class, size, age, location, construction and other factors used in the local assessment process. Nearby does not automatically mean comparable.
Similar does not mean identical, and a difference among comparable assessments is evidence to evaluate rather than a verdict. The responsible assessing or appeal authority decides how much weight the evidence carries.