Attrition can be a bit of a red herring: any organization, to remain healthy, requires new intake. A hierarchical organization like the CF which is largely closed to lateral intake even more so - the CF doesn't hire Majors or Warrant officers off the street.
Thus, the question should be "What rate of attrition at what rank levels is needed, for each occupation in the CF?" Any fixation on short-term may result in sub-optimal results. An occupation may appear "healthy" but in fact have many people about to enter traditional exit gates (end of VIE, CE or IE, or reaching the 20 /25 pensionable points) and thus be at risk and need intake; other occupations may appear to be short but have a large BTL nearing the OFP and thus not require significant intake.
Infantryman is a different situation. It's an occupation where the CF can afford to take some risk, as the entry requirements are not onerous, the training is straightforward and relatively short, and there is large depth in the Primary Reserve for augmentation if required. Thus, deficits at the Pte/Cpl rank in the Reg F infantryman occupation may be an acceptable area of risk for the CF writ large.