Probably not. Prosperity is affected by a ton of thing, including very importantly, the prosperity level itself. Temporary prosperity bonuses are applied last (after prosperity is adjusted for actions, events, and taxes).
Defiant has -2 prosperity modifier.
So, It started at Defiant (2).
Fair Taxes has a modifier of 0 (no effect on prosperity).
Defiant prosperity has a -2 modifier (0).
Therefore, the province is reduced to Rebellion (0), but the temporary bonus raises it 1 level and bless raised it 1 level. Putting it back at defiant...temporarily anyways.