We have a leak from the tub into the ceiling below. I'm pretty sure it's from the overflow drain, but as soon as the home warranty plumber heard this he said "oh, that's the problem, the overflow gasket is not designed to take that much water" and basically washed his hands of the issue (and emphasized his great experience as a master plumber vs. mine [none]).
But this sounds crazy to me: my expectation is that an overflow drain should be able to take as much water as will flow through it without leaking. I agree it may not be able to prevent the tub from overtopping, but I do expect it should not leak unless you're pointing a pressure washer nozzle through it or something.
So am I crazy, or is he?