Something just doesn't sound right. Are you absolutely positively sure that it's the pan gasket and only the pan gasket that's leaking? How flat does the pan sit on the gasket surface when there's no gasket there? Have you cleaned the gasket surfaces on both the pan and the transmission with alcohol before using the gasket sealer (possibly overkill but the gasket sealer doesn't seal well if there's grease or oil on the surface)?

I'm thinking that unless the pan is significantly bent out of shape, the gasket & gasket sealer should seal up any minor irregularities. Since it's not doing that, there has to be something else wrong - a crack in the pan or transmission case, the leak not actually being from the pan gasket itself, or something else really unusual.