or you could make it so we take damage from our own aoe spells then it would be a moot point. Also it might mean people would use a wider variety of spells. Standing in your own (or your partymember's) firewall/bladebarrier/etc ... I can't deny the effectiveness or efficiency at which they work, but I also can't say it has ever added to my enjoyment of the game.
Of course I realize more people would hate this idea than would love it, and I don't expect to see it happen.