The fairness safeguard that already exists is the appeal process. The Saskatchewan Assessment Management Agency's mass appraisal model can misjudge an individual property, high value or not, and the Board of Revision exists specifically to correct an assessment that is out of line with what comparable properties actually sold for.
A higher-value home is more likely to have unique features, a larger lot or an unpermitted improvement that a mass appraisal model handles poorly in either direction, so an owner of that kind of property has more reason than most to check the assessment against real sale evidence rather than assume it is correct.
The most useful fairness check for a specific Saskatoon property is a market-based valuation, not a policy debate. Get your hand-reviewed valuation from Joel Dyck.