I respectfully disagree.
"Tanking" in D&D doesnt work like in the average MMO, where the Tank has to have the highest AC to function properly.
In Fact, at a certain point, maxing your defenses as the "tank" can be quite bad for your party. The reason is that - unlike in an MMO - even with fighter marks an the like, the enemy still in general can choose freely who he want`s to attack. He just has to be willing to live with the consequences if he is going to ignore the tank (e.g. getting a -2 penalty on attacks and an extra attack of the fighter)
Now, if the fighter has a very high ac and little damage output like you suggest, why shouldn`t the enemy try ignore him an go directly for the striker or healer? Even with -2 on his attacks, he`ll still be hitting the striker more often than the high ac tank. And the little extra damage from the fighters extra attacks doesn`t offset the advantage of getting rid of the striker/healer sooner (or letting the party waste ressources to save them).
That said, I`d say the "ideal" Tank in most situations should have defenses about on the same level as the party average, he shoud deal decent damage and have lot`ts of hp and healing surges in order to be able to get healed very efficiently. Being able to selfheal helps as well.
p.s. Just to make it clear, I don`t think that anyone should "force" another player into a certain role. Luckily, this isnt a MMO, where encounters are fixed, and certain playstyles are "required" by the game. As a DM, I am always planning my encounters according to my gaming groups composition.