A jump in assessed value is not automatically wrong. The City of Saskatoon reassesses on a cycle, and a neighbourhood with strong recent sales will see its assessments rise to match, which is normal rather than an error. What you are checking is whether your home's new figure lines up with comparable sales, not whether the number went up at all.
If the increase came from a permitted renovation being added to the roll, remember the same permit record is exactly what a buyer's lawyer and a lender's appraiser will want later, since documented improvements support market value the way they now support the assessment. An appeal only changes the tax base, calculated on 80 percent of assessed value under Saskatchewan's residential percentage of value.
If you are selling soon, the assessment fight matters less than getting the market number right before you list. Get your hand-reviewed valuation from Joel Dyck.