Trailforums has an informative thread on pitching your tent in a downpour.
I’ve been tempted to try out my REI Quarter Dome on a rainy weekend just to see how it’s done, but I’m not sure I want to get all cold and wet just to prove a point. The Quarter Dome, as one poster on the TF thread notes, has Velcro tabs to attach the fly to the inner tent so you can set both parts up at once and presumably keep the inner mesh dry even in the rain.
This is one area where a tarp has an advantage over a tent: you string the thing up and you’ve got an instant highway overpass to get yourself and your gear in out of the deluge.
Once I figured out how to pitch a big, double-walled tent in a pouring rain storm without soaking the inside (and the ones like Hilleberg’s tents that were designed for this in the first place don’t count), I discovered that pitching a poncho-tarp in similar conditions was actually easier and quicker.