I have a Sprayway Goretex jacket that is about 10 years old and has always kept me bone dry. It has never been treated, and not particularly well kept, being shoved in the rucksack when not needed. So it sounds like something is wrong.
Your friend is right about the breathabililty suffering if the fabric is soaked, as the micropores get blocked, but it still shouldn't let the rain in, but you may get wet from internal condensation. For the same reason you have to be careful with any additional waterproofing agent you apply as these might also block the pores. Even when the pores are clear, it can only allow moisture through at a certain rate, so if you were marching up scarfell pike and sweating like a pig, you're still gonna get wet.
My jacket is 3 ply (the goretex layer is sandwiched in between 2 other nylon layers. Some jackets are only 2 ply and are more fragile, and heavy wear & tear could cause the goretex layer to break up and fail.
Check the seams as well of course.
Other than that it sounds like a manufacturing problem and should be returned I think.