I am enchanted by this notion of taunting as magical mind control rather than simply insulting an ogre’s mother. One aspect of 4th Edition Dungeons and Dragons is dividing power source and role. A Wizard is an arcane controller, a Fighter is a martial defender, and a Swordmage is an arcane defender. If you want a taunt ability, you could build it as psychological trickery, a magical compulsion, a divine geas, or a psychic power. They all amount to roughly the same thing, but it goes with my favorite notion of detaching the mechanics from the fluff. This is a martial class, so it gets martial fluff, while those magical tanks get magical fluff.
Update with additional thought: D&D 4E also avoids the taunting question by using a mechanic called “marking.” A marked target is free to attack whoever it wants, but if the attack does not include the marking defender, it has a penalty to hit, and all the defenders get to do something extra in that case. You can ignore the tank, at which point the tank becomes a pretty good debuffing class that is free to go with its secondary function (generally damage).