Yes I agree that many pathogens can be lethal, but more often that they are not. Take chytrid for example, it is devastating populations in the tropics, but outside of the tropics most amphibians are living with the infection and does not always develop chytridiomycosis, the lethal disease. How do I know that? There is plentiful evidence that chytrid is globally distributed to the point that if there's amphibian, there's chytrid, and yet records of mass extinction and population declines have only been observed in the tropics. What about those that are infected in the neotropics and temperate zone? Many of them live with the infection. Ranavirus is another good example of a potentially lethal pathogen that are not usually lethal.

Ceratophrys species on the one hand, are definitely vulnerable to chytridiomycosis. So I'm afraid chytrid infection will yield to high percentage of death.

edit: one question worth asking would be when a pathogen (e.g. chytrid) becomes pathogenic (e.g. Pathogenic).