As a tank, I'd like to remind you there is a flipside to this coin as well.

I've had a number of duty finder parties, and it seems in almost ALL of them, I have to scramble to keep people alive, because EVERYONE is attacking a different target. If I switch to a target someone is on, they switch to another, and NO amount of Flash spam is going to keep up with a Black Mage throwing AoE nukes as fast as he can. When someone gets aggro, especially archers, their response is almost universally to backpedal as fast as they can, while still frantically firing at the mob. This ensures the mob is out of Flash range by the time it goes off. I've had group members run in to the boss, open with the Limit Break, and then ask me if I knew how to tank when they got hit... all before I even got in range to provoke it (Again, archer).

I'm not contesting there are awful tanks out there, but keep in mind, there is more than enough awful to go around in ALL categories.