I won't comment on the level or the appropriateness.... I'll let the CRA officials determine whether they have sufficient resources to pursue all the audits they should be pursuing.
It's certainly the case that audits are a very important way of addressing the tax gap and narrowing it to the extent possible, because audits, first of all, uncover tax evasion. Also, and I think equally important, they provide a disincentive to engage in the behaviour in the first place. If there's a relatively high likelihood of getting caught, it's a disincentive to engaging in the behaviour in the first place.