For me, it depends on the weather and the pack. (Having said that, I'll add a general caveat that the lighter the load - say, under 25 pounds - the less the weight distribution matters, because there's just not that much weight.)

Weather: on a fine, sunny day my tent will migrate into the middle third of the pack, since it won't matter a whole lot if I have to take other stuff out to get to it. On a cold day, a jacket or other clothing I might want during the day goes on top. If it looks like rain, the tent will go just under the rain jacket.

Type of pack: If I'm using an ultralight pack (like the Granite Gear Vapor Trail or Virga), which usually has only two side pockets but no lid pocket, the tent almost never goes on top: rain gear and clothes, first aid kit, toilet paper, or water filter go on top since I'll need them during the day. The tent usually goes just underneath this stuff (which falls easily out of the way to let the tent out when its raining); lunch and snacks go in a side pocket with maps. If I'm using a more traditional pack (like an Aether 60), the tent is usually in the top of the main pack. Rain gear goes in the shove-it pocket; water, filter, and snacks go in the side pockets; and maps, first aid kit, toilet paper, and small clothing items like gloves and caps go in the lid compartment.

I also split my tent into two smaller stuff sacks, one for the fly and one for the body. This keeps a wet fly separated from the inner tent, and makes it a little easier to pack (stack them vertical, or side by side, as the mood strikes or logic dictates.)