Don't get me wrong, I know that the tarp-tent combination will work, but it's just not the way I like to set up camp. There is definitely a place for tarps when setting up camp, but to provide a dry area in addition to the tent (like the "kitchen"), not as a way to keep the tent dry. In my brain a tarp over a tent is like wearing a poncho over top of rain jacket & pants. Again, this is just my preference, I'd never say that someone shouldn't do it; it's just not how I do things.

Since my preference is to have a tent that can handle the rain on its own, I've selected my gear appropriately (full fly, good material, vestibules, etc). I am confident in my tents' ability to keep me dry when they are set up and guyed out properly and they've proven themselves capable so far.