Personally I don't think positioning has anything to do with it at all. Their should be some kind of balance that prevents a team from losing all their weapons. Like make one that nobody can take.
I say this because yesterday night I was with the group in the tower. Contrary to popular belief its actually harder than you would think. The tower overlooks a vast map with countless places to hide. Even under fire the ground team has places to hide. Yes I agree it is difficult to impossible to get up. But if the ground team doesn't attempt to get up and spreads out it is near impossible to keep them down.
Yesterday, like Chrono said, someone betrayed and threw all the tower's rockets down. But no matter, its the same thing the tower has been doing right? Wrong. When ground players spawn they spawn in building safely throughout the map. When tower players spawn they all spawn in one crowded and vulnerable room. Basically all the ground players, now in control of all 8 rocket launchers, spammed shots at the small tower. The second we spawned we were killed again, and again, and again. All the firing points were set up in different areas throughout the map so we could never regain enough control to even put up a fight.
Point is. Yes, some spots are abusive to ground. But some places are also abusive to the tower. Keep in mind the ground team has a vast area to run around in and avoid fire. But the tower team has nowhere to go or even spawn.