I always considered the "tank" role as stupid unless it made tactically sense (the aforementioned corridor, for example), or if the NPCs could do the same - and telling players "No, your character will attack the heavily armored fighter, and not the weak wizard that is magic missiling you to death, because the tank taunted you" is just wrong.
I still think that terrain and tactics, not "magical" "you have to attack me and ignore the wizard" powers should determine if tanking is possible. A single fighter, in open terrain, simply can't protect a whole party of four, IMHO.