I can't agree with the description of Macbeth "dropping the ball with the porter scene". It's a darkly hilarious release of the tension in the previous scene. Macbeth is losing his mind in guilt, and then suddenly you're in a comedic relief scene, with a hungover drunkard cracking jokes about whiskey dick.

His initial monologue has perhaps not aged as gracefully, but the humor in this hungover buffoon incorporating the knocking at the gate he's supposed to be tending can be funny enough in its own right.