We can separate having any impact, e.g. on the scale of a saved life or more, in the actual world from solving a large part of the total problem. A $1 VillageReach contribution is quite unlikely to save a life, but $100,000 would be quite likely to save 100. Either way, there is little chance of making a noticeable percentage decrease in global poverty or disease rates (although there is some, e.g. by boosting the new institutions and culture of efficient philanthropy, etc). I think political contributions and funding for scientific (including medical) research would be a better comparison, where even large donations are unlikely to deliver actual results (although we think that on the whole the practice of funding medical research is quite likely to pay off, even if any particular researcher is unlikely to cure cancer, etc).

I figure Pascal's mugging additionaly requires a chance of very large utility delta being involved.